~dkuhlman/python-training-materials/Materials

floating-point numbers and for the <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a> class.

There are some useful additions to the standard library, such as a

greatly enhanced <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal">unittest</code></a> module, the <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal">argparse</code></a> module

for parsing command-line options, convenient <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal">OrderedDict</code></a>

and <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal">Counter</code></a> classes in the <a class="reference internal" href="../library/collections.html#module-collections" title="collections: High-performance datatypes"><code class="xref py py-mod docutils literal">collections</code></a> module,

and many other improvements.

Python 2.7 is planned to be the last of the 2.x releases, so we worked

on making it a good release for the long term. To help with porting

to Python 3, several new features from the Python 3.x series have been

included in 2.7.

This article doesn’t attempt to provide a complete specification of

100

the new features, but instead provides a convenient overview. For

101

full details, you should refer to the documentation for Python 2.7 at

102

<a class="reference external" href="https://docs.python.org">https://docs.python.org</a>. If you want to understand the rationale for

103

the design and implementation, refer to the PEP for a particular new

104

feature or the issue on <a class="reference external" href="https://bugs.python.org">https://bugs.python.org</a> in which a change was

105

discussed. Whenever possible, “What’s New in Python” links to the

106

bug/patch item for each change.

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<h2>The Future for Python 2.x<a class="headerlink" href="#the-future-for-python-2-x" title="Permalink to this headline">¶</a></h2>

109

Python 2.7 is the last major release in the 2.x series, as the Python

110

maintainers have shifted the focus of their new feature development efforts

111

to the Python 3.x series. This means that while Python 2 continues to

112

receive bug fixes, and to be updated to build correctly on new hardware and

113

versions of supported operated systems, there will be no new full feature

114

releases for the language or standard library.

115

However, while there is a large common subset between Python 2.7 and Python

116

3, and many of the changes involved in migrating to that common subset, or

117

directly to Python 3, can be safely automated, some other changes (notably

118

those associated with Unicode handling) may require careful consideration,

119

and preferably robust automated regression test suites, to migrate

120

effectively.

121

This means that Python 2.7 will remain in place for a long time, providing a

122

stable and supported base platform for production systems that have not yet

123

been ported to Python 3. The full expected lifecycle of the Python 2.7

124

series is detailed in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0373">PEP 373</a>.

125

Some key consequences of the long-term significance of 2.7 are:

126

127

<li>As noted above, the 2.7 release has a much longer period of maintenance

128

when compared to earlier 2.x versions. Python 2.7 is currently expected to

129

remain supported by the core development team (receiving security updates

130

and other bug fixes) until at least 2020 (10 years after its initial

131

release, compared to the more typical support period of 18-24 months).</li>

132

<li>As the Python 2.7 standard library ages, making effective use of the

133

Python Package Index (either directly or via a redistributor) becomes

134

more important for Python 2 users. In addition to a wide variety of third

135

party packages for various tasks, the available packages include backports

136

of new modules and features from the Python 3 standard library that are

137

compatible with Python 2, as well as various tools and libraries that can

138

make it easier to migrate to Python 3. The <a class="reference external" href="https://packaging.python.org">Python Packaging User Guide</a> provides guidance on downloading and

139

installing software from the Python Package Index.</li>

140

<li>While the preferred approach to enhancing Python 2 is now the publication

141

of new packages on the Python Package Index, this approach doesn’t

142

necessarily work in all cases, especially those related to network

143

security. In exceptional cases that cannot be handled adequately by

144

publishing new or updated packages on PyPI, the Python Enhancement

145

Proposal process may be used to make the case for adding new features

146

directly to the Python 2 standard library. Any such additions, and the

147

maintenance releases where they were added, will be noted in the

148

<a class="reference internal" href="#py27-maintenance-enhancements">New Features Added to Python 2.7 Maintenance Releases</a> section below.</li>

149

</ul>

150

For projects wishing to migrate from Python 2 to Python 3, or for library

151

and framework developers wishing to support users on both Python 2 and

152

Python 3, there are a variety of tools and guides available to help decide

153

on a suitable approach and manage some of the technical details involved.

154

The recommended starting point is the <a class="reference internal" href="../howto/pyporting.html#pyporting-howto">Porting Python 2 Code to Python 3</a> HOWTO guide.

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</div>

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<h2>Changes to the Handling of Deprecation Warnings<a class="headerlink" href="#changes-to-the-handling-of-deprecation-warnings" title="Permalink to this headline">¶</a></h2>

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For Python 2.7, a policy decision was made to silence warnings only of

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interest to developers by default. <a class="reference internal" href="../library/exceptions.html#exceptions.DeprecationWarning" title="exceptions.DeprecationWarning"><code class="xref py py-exc docutils literal">DeprecationWarning</code></a> and its

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descendants are now ignored unless otherwise requested, preventing

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users from seeing warnings triggered by an application. This change

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was also made in the branch that became Python 3.2. (Discussed

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on stdlib-sig and carried out in <a class="reference external" href="https://bugs.python.org/issue7319">issue 7319</a>.)

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In previous releases, <a class="reference internal" href="../library/exceptions.html#exceptions.DeprecationWarning" title="exceptions.DeprecationWarning"><code class="xref py py-exc docutils literal">DeprecationWarning</code></a> messages were

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enabled by default, providing Python developers with a clear

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indication of where their code may break in a future major version

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of Python.

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However, there are increasingly many users of Python-based

169

applications who are not directly involved in the development of

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those applications. <a class="reference internal" href="../library/exceptions.html#exceptions.DeprecationWarning" title="exceptions.DeprecationWarning"><code class="xref py py-exc docutils literal">DeprecationWarning</code></a> messages are

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irrelevant to such users, making them worry about an application

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that’s actually working correctly and burdening application developers

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with responding to these concerns.

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You can re-enable display of <a class="reference internal" href="../library/exceptions.html#exceptions.DeprecationWarning" title="exceptions.DeprecationWarning"><code class="xref py py-exc docutils literal">DeprecationWarning</code></a> messages by

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running Python with the <a class="reference internal" href="../using/cmdline.html#cmdoption-W"><code class="xref std std-option docutils literal">-Wdefault</code></a> (short form:

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<a class="reference internal" href="../using/cmdline.html#cmdoption-W"><code class="xref std std-option docutils literal">-Wd</code></a>) switch, or by setting the <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONWARNINGS"><code class="xref std std-envvar docutils literal">PYTHONWARNINGS</code></a>

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environment variable to <code class="docutils literal">"default"</code> (or <code class="docutils literal">"d"</code>) before running

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Python. Python code can also re-enable them

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by calling <code class="docutils literal">warnings.simplefilter('default')</code>.

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The <code class="docutils literal">unittest</code> module also automatically reenables deprecation warnings

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when running tests.

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</div>

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<h2>Python 3.1 Features<a class="headerlink" href="#python-3-1-features" title="Permalink to this headline">¶</a></h2>

185

Much as Python 2.6 incorporated features from Python 3.0,

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version 2.7 incorporates some of the new features

187

in Python 3.1. The 2.x series continues to provide tools

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for migrating to the 3.x series.

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A partial list of 3.1 features that were backported to 2.7:

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<li>The syntax for set literals (<code class="docutils literal">{1,2,3}</code> is a mutable set).</li>

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<li>Dictionary and set comprehensions (<code class="docutils literal">{i: i*2 for i in range(3)}</code>).</li>

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<li>Multiple context managers in a single <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal">with</code></a> statement.</li>

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<li>A new version of the <a class="reference internal" href="../library/io.html#module-io" title="io: Core tools for working with streams."><code class="xref py py-mod docutils literal">io</code></a> library, rewritten in C for performance.</li>

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<li>The ordered-dictionary type described in <a class="reference internal" href="#pep-0372">PEP 372: Adding an Ordered Dictionary to collections</a>.</li>

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<li>The new <code class="docutils literal">","</code> format specifier described in <a class="reference internal" href="#pep-0378">PEP 378: Format Specifier for Thousands Separator</a>.</li>

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<li>The <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal">memoryview</code></a> object.</li>

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<li>A small subset of the <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: Convenience wrappers for __import__"><code class="xref py py-mod docutils literal">importlib</code></a> module,

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<a class="reference external" href="#importlib-section">described below</a>.</li>

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<li>The <a class="reference internal" href="../library/functions.html#repr" title="repr"><code class="xref py py-func docutils literal">repr()</code></a> of a float <code class="docutils literal">x</code> is shorter in many cases: it’s now

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based on the shortest decimal string that’s guaranteed to round back

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to <code class="docutils literal">x</code>. As in previous versions of Python, it’s guaranteed that

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<code class="docutils literal">float(repr(x))</code> recovers <code class="docutils literal">x</code>.</li>

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<li>Float-to-string and string-to-float conversions are correctly rounded.

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The <a class="reference internal" href="../library/functions.html#round" title="round"><code class="xref py py-func docutils literal">round()</code></a> function is also now correctly rounded.</li>

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<li>The <a class="reference internal" href="../c-api/capsule.html#c.PyCapsule" title="PyCapsule"><code class="xref c c-type docutils literal">PyCapsule</code></a> type, used to provide a C API for extension modules.</li>

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<li>The <a class="reference internal" href="../c-api/long.html#c.PyLong_AsLongAndOverflow" title="PyLong_AsLongAndOverflow"><code class="xref c c-func docutils literal">PyLong_AsLongAndOverflow()</code></a> C API function.</li>

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</ul>

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Other new Python3-mode warnings include:

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<li><a class="reference internal" href="../library/operator.html#operator.isCallable" title="operator.isCallable"><code class="xref py py-func docutils literal">operator.isCallable()</code></a> and <a class="reference internal" href="../library/operator.html#operator.sequenceIncludes" title="operator.sequenceIncludes"><code class="xref py py-func docutils literal">operator.sequenceIncludes()</code></a>,

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which are not supported in 3.x, now trigger warnings.</li>

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<li>The <a class="reference internal" href="../using/cmdline.html#cmdoption-3"><code class="xref std std-option docutils literal">-3</code></a> switch now automatically

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enables the <a class="reference internal" href="../using/cmdline.html#cmdoption-Q"><code class="xref std std-option docutils literal">-Qwarn</code></a> switch that causes warnings

215

about using classic division with integers and long integers.</li>

216

</ul>

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</div>

218

219

<h2>PEP 372: Adding an Ordered Dictionary to collections<a class="headerlink" href="#pep-372-adding-an-ordered-dictionary-to-collections" title="Permalink to this headline">¶</a></h2>

220

Regular Python dictionaries iterate over key/value pairs in arbitrary order.

221

Over the years, a number of authors have written alternative implementations

222

that remember the order that the keys were originally inserted. Based on

223

the experiences from those implementations, 2.7 introduces a new

224

<a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal">OrderedDict</code></a> class in the <a class="reference internal" href="../library/collections.html#module-collections" title="collections: High-performance datatypes"><code class="xref py py-mod docutils literal">collections</code></a> module.

225

The <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal">OrderedDict</code></a> API provides the same interface as regular

226

dictionaries but iterates over keys and values in a guaranteed order

227

depending on when a key was first inserted:

228

<div class="highlight-python"><div class="highlight"><pre>>>> from collections import OrderedDict

229

>>> d = OrderedDict([('first', 1),

230

... ('second', 2),

231

... ('third', 3)])

232

>>> d.items()

233

[('first', 1), ('second', 2), ('third', 3)]

234

</pre></div>

235

</div>

236

If a new entry overwrites an existing entry, the original insertion

237

position is left unchanged:

238

<div class="highlight-python"><div class="highlight"><pre>>>> d['second'] = 4

239

>>> d.items()

240

[('first', 1), ('second', 4), ('third', 3)]

241

</pre></div>

242

</div>

243

Deleting an entry and reinserting it will move it to the end:

244

<div class="highlight-python"><div class="highlight"><pre>>>> del d['second']

245

>>> d['second'] = 5

246

>>> d.items()

247

[('first', 1), ('third', 3), ('second', 5)]

248

</pre></div>

249

</div>

250

The <a class="reference internal" href="../library/collections.html#collections.OrderedDict.popitem" title="collections.OrderedDict.popitem"><code class="xref py py-meth docutils literal">popitem()</code></a> method has an optional last

251

argument that defaults to True. If last is True, the most recently

252

added key is returned and removed; if it’s False, the

253

oldest key is selected:

254

<div class="highlight-python"><div class="highlight"><pre>>>> od = OrderedDict([(x,0) for x in range(20)])

255

>>> od.popitem()

256

(19, 0)

257

>>> od.popitem()

258

(18, 0)

259

>>> od.popitem(last=False)

260

(0, 0)

261

262

(1, 0)

263

</pre></div>

264

</div>

265

Comparing two ordered dictionaries checks both the keys and values,

266

and requires that the insertion order was the same:

267

<div class="highlight-python"><div class="highlight"><pre>>>> od1 = OrderedDict([('first', 1),

268

... ('second', 2),

269

... ('third', 3)])

270

>>> od2 = OrderedDict([('third', 3),

271

... ('first', 1),

272

... ('second', 2)])

273

>>> od1 == od2

274

False

275

>>> # Move 'third' key to the end

276

>>> del od2['third']; od2['third'] = 3

277

>>> od1 == od2

278

True

279

</pre></div>

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</div>

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Comparing an <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal">OrderedDict</code></a> with a regular dictionary

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ignores the insertion order and just compares the keys and values.

283

How does the <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal">OrderedDict</code></a> work? It maintains a

284

doubly-linked list of keys, appending new keys to the list as they’re inserted.

285

A secondary dictionary maps keys to their corresponding list node, so

286

deletion doesn’t have to traverse the entire linked list and therefore

287

remains O(1).

288

The standard library now supports use of ordered dictionaries in several

289

modules.

290

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<li>The <a class="reference internal" href="../library/configparser.html#module-ConfigParser" title="ConfigParser: Configuration file parser."><code class="xref py py-mod docutils literal">ConfigParser</code></a> module uses them by default, meaning that

292

configuration files can now be read, modified, and then written back

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in their original order.</li>

294

<li>The <a class="reference internal" href="../library/collections.html#collections.somenamedtuple._asdict" title="collections.somenamedtuple._asdict"><code class="xref py py-meth docutils literal">_asdict()</code></a> method for

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<a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal">collections.namedtuple()</code></a> now returns an ordered dictionary with the

296

values appearing in the same order as the underlying tuple indices.</li>

297

<li>The <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal">json</code></a> module’s <a class="reference internal" href="../library/json.html#json.JSONDecoder" title="json.JSONDecoder"><code class="xref py py-class docutils literal">JSONDecoder</code></a> class

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constructor was extended with an object_pairs_hook parameter to

299

allow <code class="xref py py-class docutils literal">OrderedDict</code> instances to be built by the decoder.

300

Support was also added for third-party tools like

301

<a class="reference external" href="http://pyyaml.org/">PyYAML</a>.</li>

302

</ul>

303

304

See also

305

306

<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0372">PEP 372</a> - Adding an ordered dictionary to collections</dt>

307

<dd>PEP written by Armin Ronacher and Raymond Hettinger;

308

implemented by Raymond Hettinger.</dd>

309

</dl>

310

</div>

311

</div>

312

313

<h2>PEP 378: Format Specifier for Thousands Separator<a class="headerlink" href="#pep-378-format-specifier-for-thousands-separator" title="Permalink to this headline">¶</a></h2>

314

To make program output more readable, it can be useful to add

315

separators to large numbers, rendering them as

316

18,446,744,073,709,551,616 instead of 18446744073709551616.

317

The fully general solution for doing this is the <a class="reference internal" href="../library/locale.html#module-locale" title="locale: Internationalization services."><code class="xref py py-mod docutils literal">locale</code></a> module,

318

which can use different separators (”,” in North America, ”.” in

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Europe) and different grouping sizes, but <a class="reference internal" href="../library/locale.html#module-locale" title="locale: Internationalization services."><code class="xref py py-mod docutils literal">locale</code></a> is complicated

320

to use and unsuitable for multi-threaded applications where different

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threads are producing output for different locales.

322

Therefore, a simple comma-grouping mechanism has been added to the

323

mini-language used by the <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal">str.format()</code></a> method. When

324

formatting a floating-point number, simply include a comma between the

325

width and the precision:

326

<div class="highlight-python"><div class="highlight"><pre>>>> '{:20,.2f}'.format(18446744073709551616.0)

327

'18,446,744,073,709,551,616.00'

328

</pre></div>

329

</div>

330

When formatting an integer, include the comma after the width:

331

<div class="highlight-python"><div class="highlight"><pre>>>> '{:20,d}'.format(18446744073709551616)

332

'18,446,744,073,709,551,616'

333

</pre></div>

334

</div>

335

This mechanism is not adaptable at all; commas are always used as the

336

separator and the grouping is always into three-digit groups. The

337

comma-formatting mechanism isn’t as general as the <a class="reference internal" href="../library/locale.html#module-locale" title="locale: Internationalization services."><code class="xref py py-mod docutils literal">locale</code></a>

338

module, but it’s easier to use.

339

340

See also

341

342

<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0378">PEP 378</a> - Format Specifier for Thousands Separator</dt>

343

<dd>PEP written by Raymond Hettinger; implemented by Eric Smith.</dd>

344

</dl>

345

</div>

346

</div>

347

348

<h2>PEP 389: The argparse Module for Parsing Command Lines<a class="headerlink" href="#pep-389-the-argparse-module-for-parsing-command-lines" title="Permalink to this headline">¶</a></h2>

349

The <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal">argparse</code></a> module for parsing command-line arguments was

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added as a more powerful replacement for the

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<a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal">optparse</code></a> module.

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This means Python now supports three different modules for parsing

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command-line arguments: <a class="reference internal" href="../library/getopt.html#module-getopt" title="getopt: Portable parser for command line options; support both short and long option names."><code class="xref py py-mod docutils literal">getopt</code></a>, <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal">optparse</code></a>, and

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<a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal">argparse</code></a>. The <a class="reference internal" href="../library/getopt.html#module-getopt" title="getopt: Portable parser for command line options; support both short and long option names."><code class="xref py py-mod docutils literal">getopt</code></a> module closely resembles the C

355

library’s <code class="xref c c-func docutils literal">getopt()</code> function, so it remains useful if you’re writing a

356

Python prototype that will eventually be rewritten in C.

357

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because there are many scripts still using it, and there’s no

359

automated way to update these scripts. (Making the <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal">argparse</code></a>

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API consistent with <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal">optparse</code></a>‘s interface was discussed but

361

rejected as too messy and difficult.)

362

In short, if you’re writing a new script and don’t need to worry

363

about compatibility with earlier versions of Python, use

364

<a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal">argparse</code></a> instead of <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal">optparse</code></a>.

365

Here’s an example:

366

<div class="highlight-python"><div class="highlight"><pre>import argparse

367

368

parser = argparse.ArgumentParser(description='Command-line example.')

369

370

# Add optional switches

371

parser.add_argument('-v', action='store_true', dest='is_verbose',

372

help='produce verbose output')

373

parser.add_argument('-o', action='store', dest='output',

374

metavar='FILE',

375

help='direct output to FILE instead of stdout')

376

parser.add_argument('-C', action='store', type=int, dest='context',

377

metavar='NUM', default=0,

378

help='display NUM lines of added context')

379

380

# Allow any number of additional arguments.

381

parser.add_argument(nargs='*', action='store', dest='inputs',

382

help='input filenames (default is stdin)')

383

384

args = parser.parse_args()

385

print args.__dict__

386

</pre></div>

387

</div>

388

Unless you override it, <a class="reference internal" href="../using/cmdline.html#cmdoption-h"><code class="xref std std-option docutils literal">-h</code></a> and <a class="reference internal" href="../using/cmdline.html#cmdoption--help"><code class="xref std std-option docutils literal">--help</code></a> switches

389

are automatically added, and produce neatly formatted output:

390

<div class="highlight-python"><div class="highlight"><pre>-> ./python.exe argparse-example.py --help

391

usage: argparse-example.py [-h] [-v] [-o FILE] [-C NUM] [inputs [inputs ...]]

392

393

Command-line example.

394

395

positional arguments:

396

inputs input filenames (default is stdin)

397

398

optional arguments:

399

-h, --help show this help message and exit

400

-v produce verbose output

401

-o FILE direct output to FILE instead of stdout

402

-C NUM display NUM lines of added context

403

</pre></div>

404

</div>

405

As with <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal">optparse</code></a>, the command-line switches and arguments

406

are returned as an object with attributes named by the dest parameters:

407

<div class="highlight-python"><div class="highlight"><pre>-> ./python.exe argparse-example.py -v

408

{'output': None,

409

'is_verbose': True,

410

'context': 0,

411

'inputs': []}

412

413

-> ./python.exe argparse-example.py -v -o /tmp/output -C 4 file1 file2

414

{'output': '/tmp/output',

415

'is_verbose': True,

416

'context': 4,

417

'inputs': ['file1', 'file2']}

418

</pre></div>

419

</div>

420

<a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal">argparse</code></a> has much fancier validation than <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal">optparse</code></a>; you

421

can specify an exact number of arguments as an integer, 0 or more

422

arguments by passing <code class="docutils literal">'*'</code>, 1 or more by passing <code class="docutils literal">'+'</code>, or an

423

optional argument with <code class="docutils literal">'?'</code>. A top-level parser can contain

424

sub-parsers to define subcommands that have different sets of

425

switches, as in <code class="docutils literal">svn commit</code>, <code class="docutils literal">svn checkout</code>, etc. You can

426

specify an argument’s type as <a class="reference internal" href="../library/argparse.html#argparse.FileType" title="argparse.FileType"><code class="xref py py-class docutils literal">FileType</code></a>, which will

427

automatically open files for you and understands that <code class="docutils literal">'-'</code> means

428

standard input or output.

429

430

See also

431

432

<dt><a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal">argparse</code></a> documentation</dt>

433

<dd>The documentation page of the argparse module.</dd>

434

<dt><a class="reference internal" href="../library/argparse.html#argparse-from-optparse">Upgrading optparse code</a></dt>

435

<dd>Part of the Python documentation, describing how to convert

436

code that uses <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal">optparse</code></a>.</dd>

437

<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0389">PEP 389</a> - argparse - New Command Line Parsing Module</dt>

438

<dd>PEP written and implemented by Steven Bethard.</dd>

439

</dl>

440

</div>

441

</div>

442

443

<h2>PEP 391: Dictionary-Based Configuration For Logging<a class="headerlink" href="#pep-391-dictionary-based-configuration-for-logging" title="Permalink to this headline">¶</a></h2>

444

The <a class="reference internal" href="../library/logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal">logging</code></a> module is very flexible; applications can define

445

a tree of logging subsystems, and each logger in this tree can filter

446

out certain messages, format them differently, and direct messages to

447

a varying number of handlers.

448

All this flexibility can require a lot of configuration. You can

449

write Python statements to create objects and set their properties,

450

but a complex set-up requires verbose but boring code.

451

<a class="reference internal" href="../library/logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal">logging</code></a> also supports a <code class="xref py py-func docutils literal">fileConfig()</code>

452

function that parses a file, but the file format doesn’t support

453

configuring filters, and it’s messier to generate programmatically.

454

Python 2.7 adds a <code class="xref py py-func docutils literal">dictConfig()</code> function that

455

uses a dictionary to configure logging. There are many ways to

456

produce a dictionary from different sources: construct one with code;

457

parse a file containing JSON; or use a YAML parsing library if one is

458

installed. For more information see <a class="reference internal" href="../library/logging.config.html#logging-config-api">Configuration functions</a>.

459

The following example configures two loggers, the root logger and a

460

logger named “network”. Messages sent to the root logger will be

461

sent to the system log using the syslog protocol, and messages

462

to the “network” logger will be written to a <code class="file docutils literal">network.log</code> file

463

that will be rotated once the log reaches 1MB.

464

<div class="highlight-python"><div class="highlight"><pre>import logging

465

import logging.config

466

467

configdict = {

468

'version': 1, # Configuration schema in use; must be 1 for now

469

'formatters': {

470

'standard': {

471

'format': ('%(asctime)s %(name)-15s '

472

'%(levelname)-8s %(message)s')}},

473

474

'handlers': {'netlog': {'backupCount': 10,

475

'class': 'logging.handlers.RotatingFileHandler',

476

'filename': '/logs/network.log',

477

'formatter': 'standard',

478

'level': 'INFO',

479

'maxBytes': 1000000},

480

'syslog': {'class': 'logging.handlers.SysLogHandler',

481

'formatter': 'standard',

482

'level': 'ERROR'}},

483

484

# Specify all the subordinate loggers

485

'loggers': {

486

'network': {

487

'handlers': ['netlog']

488

}

489

},

490

# Specify properties of the root logger

491

'root': {

492

'handlers': ['syslog']

493

},

494

}

495

496

# Set up configuration

497

logging.config.dictConfig(configdict)

498

499

# As an example, log two error messages

500

logger = logging.getLogger('/')

501

logger.error('Database not found')

502

503

netlogger = logging.getLogger('network')

504

netlogger.error('Connection failed')

505

</pre></div>

506

</div>

507

Three smaller enhancements to the <a class="reference internal" href="../library/logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal">logging</code></a> module, all

508

implemented by Vinay Sajip, are:

509

510

<li>The <a class="reference internal" href="../library/logging.handlers.html#logging.handlers.SysLogHandler" title="logging.handlers.SysLogHandler"><code class="xref py py-class docutils literal">SysLogHandler</code></a> class now supports

511

syslogging over TCP. The constructor has a socktype parameter

512

giving the type of socket to use, either <a class="reference internal" href="../library/socket.html#socket.SOCK_DGRAM" title="socket.SOCK_DGRAM"><code class="xref py py-const docutils literal">socket.SOCK_DGRAM</code></a>

513

for UDP or <a class="reference internal" href="../library/socket.html#socket.SOCK_STREAM" title="socket.SOCK_STREAM"><code class="xref py py-const docutils literal">socket.SOCK_STREAM</code></a> for TCP. The default

514

protocol remains UDP.</li>

515

<li><a class="reference internal" href="../library/logging.html#logging.Logger" title="logging.Logger"><code class="xref py py-class docutils literal">Logger</code></a> instances gained a <a class="reference internal" href="../library/logging.html#logging.Logger.getChild" title="logging.Logger.getChild"><code class="xref py py-meth docutils literal">getChild()</code></a>

516

method that retrieves a descendant logger using a relative path.

517

For example, once you retrieve a logger by doing <code class="docutils literal">log = getLogger('app')</code>,

518

calling <code class="docutils literal">log.getChild('network.listen')</code> is equivalent to

519

<code class="docutils literal">getLogger('app.network.listen')</code>.</li>

520

<li>The <a class="reference internal" href="../library/logging.html#logging.LoggerAdapter" title="logging.LoggerAdapter"><code class="xref py py-class docutils literal">LoggerAdapter</code></a> class gained a

521

<code class="xref py py-meth docutils literal">isEnabledFor()</code> method that takes a

522

level and returns whether the underlying logger would

523

process a message of that level of importance.</li>

524

</ul>

525

526

See also

527

528

<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0391">PEP 391</a> - Dictionary-Based Configuration For Logging</dt>

529

<dd>PEP written and implemented by Vinay Sajip.</dd>

530

</dl>

531

</div>

532

</div>

533

534

<h2>PEP 3106: Dictionary Views<a class="headerlink" href="#pep-3106-dictionary-views" title="Permalink to this headline">¶</a></h2>

535

The dictionary methods <a class="reference internal" href="../library/stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal">keys()</code></a>, <a class="reference internal" href="../library/stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal">values()</code></a>, and

536

<a class="reference internal" href="../library/stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal">items()</code></a> are different in Python 3.x. They return an object

537

called a view instead of a fully materialized list.

538

It’s not possible to change the return values of <a class="reference internal" href="../library/stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal">keys()</code></a>,

539

<a class="reference internal" href="../library/stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal">values()</code></a>, and <a class="reference internal" href="../library/stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal">items()</code></a> in Python 2.7 because

540

too much code would break. Instead the 3.x versions were added

541

under the new names <a class="reference internal" href="../library/stdtypes.html#dict.viewkeys" title="dict.viewkeys"><code class="xref py py-meth docutils literal">viewkeys()</code></a>, <a class="reference internal" href="../library/stdtypes.html#dict.viewvalues" title="dict.viewvalues"><code class="xref py py-meth docutils literal">viewvalues()</code></a>,

542

and <a class="reference internal" href="../library/stdtypes.html#dict.viewitems" title="dict.viewitems"><code class="xref py py-meth docutils literal">viewitems()</code></a>.

543

<div class="highlight-python"><div class="highlight"><pre>>>> d = dict((i*10, chr(65+i)) for i in range(26))

544

>>> d

545

{0: 'A', 130: 'N', 10: 'B', 140: 'O', 20: ..., 250: 'Z'}

546

>>> d.viewkeys()

547

dict_keys([0, 130, 10, 140, 20, 150, 30, ..., 250])

548

</pre></div>

549

</div>

550

Views can be iterated over, but the key and item views also behave

551

like sets. The <code class="docutils literal">&</code> operator performs intersection, and <code class="docutils literal">|</code>

552

performs a union:

553

<div class="highlight-python"><div class="highlight"><pre>>>> d1 = dict((i*10, chr(65+i)) for i in range(26))

554

>>> d2 = dict((i**.5, i) for i in range(1000))

555

>>> d1.viewkeys() & d2.viewkeys()

556

set([0.0, 10.0, 20.0, 30.0])

557

>>> d1.viewkeys() | range(0, 30)

558

set([0, 1, 130, 3, 4, 5, 6, ..., 120, 250])

559

</pre></div>

560

</div>

561

The view keeps track of the dictionary and its contents change as the

562

dictionary is modified:

563

<div class="highlight-python"><div class="highlight"><pre>>>> vk = d.viewkeys()

564

>>> vk

565

dict_keys([0, 130, 10, ..., 250])

566

>>> d[260] = '&'

567

>>> vk

568

dict_keys([0, 130, 260, 10, ..., 250])

569

</pre></div>

570

</div>

571

However, note that you can’t add or remove keys while you’re iterating

572

over the view:

573

<div class="highlight-python"><div class="highlight"><pre>>>> for k in vk:

574

... d[k*2] = k

575

...

576

Traceback (most recent call last):

577

File "<stdin>", line 1, in <module>

578

RuntimeError: dictionary changed size during iteration

579

</pre></div>

580

</div>

581

You can use the view methods in Python 2.x code, and the 2to3

582

converter will change them to the standard <a class="reference internal" href="../library/stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal">keys()</code></a>,

583

584

585

See also

586

587

<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-3106">PEP 3106</a> - Revamping dict.keys(), .values() and .items()</dt>

588

<dd>PEP written by Guido van Rossum.

589

Backported to 2.7 by Alexandre Vassalotti; <a class="reference external" href="https://bugs.python.org/issue1967">issue 1967</a>.</dd>

590

</dl>

591

</div>

592

</div>

593

594

<h2>PEP 3137: The memoryview Object<a class="headerlink" href="#pep-3137-the-memoryview-object" title="Permalink to this headline">¶</a></h2>

595

The <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal">memoryview</code></a> object provides a view of another object’s

596

memory content that matches the <code class="xref py py-class docutils literal">bytes</code> type’s interface.

597

<div class="highlight-python"><div class="highlight"><pre>>>> import string

598

>>> m = memoryview(string.letters)

599

>>> m

600

601

>>> len(m) # Returns length of underlying object

602

52

603

>>> m[0], m[25], m[26] # Indexing returns one byte

604

('a', 'z', 'A')

605

>>> m2 = m[0:26] # Slicing returns another memoryview

606

>>> m2

607

608

</pre></div>

609

</div>

610

The content of the view can be converted to a string of bytes or

611

a list of integers:

612

<div class="highlight-python"><div class="highlight"><pre>>>> m2.tobytes()

613

'abcdefghijklmnopqrstuvwxyz'

614

>>> m2.tolist()

615

[97, 98, 99, 100, 101, 102, 103, ... 121, 122]

616

>>>

617

</pre></div>

618

</div>

619

<a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal">memoryview</code></a> objects allow modifying the underlying object if

620

it’s a mutable object.

621

<div class="highlight-python"><div class="highlight"><pre>>>> m2[0] = 75

622

Traceback (most recent call last):

623

File "<stdin>", line 1, in <module>

624

TypeError: cannot modify read-only memory

625

>>> b = bytearray(string.letters) # Creating a mutable object

626

>>> b

627

bytearray(b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')

628

>>> mb = memoryview(b)

629

>>> mb[0] = '*' # Assign to view, changing the bytearray.

630

>>> b[0:5] # The bytearray has been changed.

631

bytearray(b'*bcde')

632

>>>

633

</pre></div>

634

</div>

635

636

See also

637

638

<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-3137">PEP 3137</a> - Immutable Bytes and Mutable Buffer</dt>

639

<dd>PEP written by Guido van Rossum.

640

Implemented by Travis Oliphant, Antoine Pitrou and others.

641

Backported to 2.7 by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue2396">issue 2396</a>.</dd>

642

</dl>

643

</div>

644

</div>

645

646

<h2>Other Language Changes<a class="headerlink" href="#other-language-changes" title="Permalink to this headline">¶</a></h2>

647

Some smaller changes made to the core Python language are:

648

<ul>

649

<li>The syntax for set literals has been backported from Python 3.x.

650

Curly brackets are used to surround the contents of the resulting

651

mutable set; set literals are

652

distinguished from dictionaries by not containing colons and values.

653

<code class="docutils literal">{}</code> continues to represent an empty dictionary; use

654

<code class="docutils literal">set()</code> for an empty set.

655

<div class="highlight-python"><div class="highlight"><pre>>>> {1, 2, 3, 4, 5}

656

set([1, 2, 3, 4, 5])

657

>>> set() # empty set

658

set([])

659

>>> {} # empty dict

660

{}

661

</pre></div>

662

</div>

663

Backported by Alexandre Vassalotti; <a class="reference external" href="https://bugs.python.org/issue2335">issue 2335</a>.

664

</li>

665

<li>Dictionary and set comprehensions are another feature backported from

666

3.x, generalizing list/generator comprehensions to use

667

the literal syntax for sets and dictionaries.

668

<div class="highlight-python"><div class="highlight"><pre>>>> {x: x*x for x in range(6)}

669

{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25}

670

>>> {('a'*x) for x in range(6)}

671

set(['', 'a', 'aa', 'aaa', 'aaaa', 'aaaaa'])

672

</pre></div>

673

</div>

674

Backported by Alexandre Vassalotti; <a class="reference external" href="https://bugs.python.org/issue2333">issue 2333</a>.

675

</li>

676

<li>The <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal">with</code></a> statement can now use multiple context managers

677

in one statement. Context managers are processed from left to right

678

and each one is treated as beginning a new <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal">with</code></a> statement.

679

This means that:

680

<div class="highlight-python"><div class="highlight"><pre>with A() as a, B() as b:

681

... suite of statements ...

682

</pre></div>

683

</div>

684

is equivalent to:

685

686

with B() as b:

687

... suite of statements ...

688

</pre></div>

689

</div>

690

The <a class="reference internal" href="../library/contextlib.html#contextlib.nested" title="contextlib.nested"><code class="xref py py-func docutils literal">contextlib.nested()</code></a> function provides a very similar

691

function, so it’s no longer necessary and has been deprecated.

692

(Proposed in <a class="reference external" href="https://codereview.appspot.com/53094">https://codereview.appspot.com/53094</a>; implemented by

693

Georg Brandl.)

694

</li>

695

<li>Conversions between floating-point numbers and strings are

696

now correctly rounded on most platforms. These conversions occur

697

in many different places: <a class="reference internal" href="../library/functions.html#str" title="str"><code class="xref py py-func docutils literal">str()</code></a> on

698

floats and complex numbers; the <a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal">float</code></a> and <a class="reference internal" href="../library/functions.html#complex" title="complex"><code class="xref py py-class docutils literal">complex</code></a>

699

constructors;

700

numeric formatting; serializing and

701

deserializing floats and complex numbers using the

702

<a class="reference internal" href="../library/marshal.html#module-marshal" title="marshal: Convert Python objects to streams of bytes and back (with different constraints)."><code class="xref py py-mod docutils literal">marshal</code></a>, <a class="reference internal" href="../library/pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal">pickle</code></a>

703

and <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal">json</code></a> modules;

704

parsing of float and imaginary literals in Python code;

705

and <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a>-to-float conversion.

706

Related to this, the <a class="reference internal" href="../library/functions.html#repr" title="repr"><code class="xref py py-func docutils literal">repr()</code></a> of a floating-point number x

707

now returns a result based on the shortest decimal string that’s

708

guaranteed to round back to x under correct rounding (with

709

round-half-to-even rounding mode). Previously it gave a string

710

based on rounding x to 17 decimal digits.

711

The rounding library responsible for this improvement works on

712

Windows and on Unix platforms using the gcc, icc, or suncc

713

compilers. There may be a small number of platforms where correct

714

operation of this code cannot be guaranteed, so the code is not

715

used on such systems. You can find out which code is being used

716

by checking <a class="reference internal" href="../library/sys.html#sys.float_repr_style" title="sys.float_repr_style"><code class="xref py py-data docutils literal">sys.float_repr_style</code></a>, which will be <code class="docutils literal">short</code>

717

if the new code is in use and <code class="docutils literal">legacy</code> if it isn’t.

718

Implemented by Eric Smith and Mark Dickinson, using David Gay’s

719

<code class="file docutils literal">dtoa.c</code> library; <a class="reference external" href="https://bugs.python.org/issue7117">issue 7117</a>.

720

</li>

721

<li>Conversions from long integers and regular integers to floating

722

point now round differently, returning the floating-point number

723

closest to the number. This doesn’t matter for small integers that

724

can be converted exactly, but for large numbers that will

725

unavoidably lose precision, Python 2.7 now approximates more

726

closely. For example, Python 2.6 computed the following:

727

<div class="highlight-python"><div class="highlight"><pre>>>> n = 295147905179352891391

728

>>> float(n)

729

2.9514790517935283e+20

730

>>> n - long(float(n))

731

65535L

732

</pre></div>

733

</div>

734

Python 2.7’s floating-point result is larger, but much closer to the

735

true value:

736

<div class="highlight-python"><div class="highlight"><pre>>>> n = 295147905179352891391

737

>>> float(n)

738

2.9514790517935289e+20

739

740

-1L

741

</pre></div>

742

</div>

743

(Implemented by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue3166">issue 3166</a>.)

744

Integer division is also more accurate in its rounding behaviours. (Also

745

implemented by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue1811">issue 1811</a>.)

746

</li>

747

<li>Implicit coercion for complex numbers has been removed; the interpreter

748

will no longer ever attempt to call a <a class="reference internal" href="../reference/datamodel.html#object.__coerce__" title="object.__coerce__"><code class="xref py py-meth docutils literal">__coerce__()</code></a> method on complex

749

objects. (Removed by Meador Inge and Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue5211">issue 5211</a>.)

750

</li>

751

<li>The <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal">str.format()</code></a> method now supports automatic numbering of the replacement

752

fields. This makes using <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal">str.format()</code></a> more closely resemble using

753

<code class="docutils literal">%s</code> formatting:

754

<div class="highlight-python"><div class="highlight"><pre>>>> '{}:{}:{}'.format(2009, 04, 'Sunday')

755

'2009:4:Sunday'

756

>>> '{}:{}:{day}'.format(2009, 4, day='Sunday')

757

'2009:4:Sunday'

758

</pre></div>

759

</div>

760

The auto-numbering takes the fields from left to right, so the first <code class="docutils literal">{...}</code>

761

specifier will use the first argument to <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal">str.format()</code></a>, the next

762

specifier will use the next argument, and so on. You can’t mix auto-numbering

763

and explicit numbering – either number all of your specifier fields or none

764

of them – but you can mix auto-numbering and named fields, as in the second

765

example above. (Contributed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue5237">issue 5237</a>.)

766

Complex numbers now correctly support usage with <a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-func docutils literal">format()</code></a>,

767

and default to being right-aligned.

768

Specifying a precision or comma-separation applies to both the real

769

and imaginary parts of the number, but a specified field width and

770

alignment is applied to the whole of the resulting <code class="docutils literal">1.5+3j</code>

771

output. (Contributed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue1588">issue 1588</a> and <a class="reference external" href="https://bugs.python.org/issue7988">issue 7988</a>.)

772

The ‘F’ format code now always formats its output using uppercase characters,

773

so it will now produce ‘INF’ and ‘NAN’.

774

(Contributed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue3382">issue 3382</a>.)

775

A low-level change: the <code class="xref py py-meth docutils literal">object.__format__()</code> method now triggers

776

a <a class="reference internal" href="../library/exceptions.html#exceptions.PendingDeprecationWarning" title="exceptions.PendingDeprecationWarning"><code class="xref py py-exc docutils literal">PendingDeprecationWarning</code></a> if it’s passed a format string,

777

because the <code class="xref py py-meth docutils literal">__format__()</code> method for <a class="reference internal" href="../library/functions.html#object" title="object"><code class="xref py py-class docutils literal">object</code></a> converts

778

the object to a string representation and formats that. Previously

779

the method silently applied the format string to the string

780

representation, but that could hide mistakes in Python code. If

781

you’re supplying formatting information such as an alignment or

782

precision, presumably you’re expecting the formatting to be applied

783

in some object-specific way. (Fixed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue7994">issue 7994</a>.)

784

</li>

785

<li>The <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-func docutils literal">int()</code></a> and <a class="reference internal" href="../library/functions.html#long" title="long"><code class="xref py py-func docutils literal">long()</code></a> types gained a <code class="docutils literal">bit_length</code>

786

method that returns the number of bits necessary to represent

787

its argument in binary:

788

<div class="highlight-python"><div class="highlight"><pre>>>> n = 37

789

>>> bin(n)

790

'0b100101'

791

>>> n.bit_length()

792

6

793

>>> n = 2**123-1

794

>>> n.bit_length()

795

123

796

>>> (n+1).bit_length()

797

124

798

</pre></div>

799

</div>

800

(Contributed by Fredrik Johansson and Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue3439">issue 3439</a>.)

801

</li>

802

<li>The <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal">import</code></a> statement will no longer try an absolute import

803

if a relative import (e.g. <code class="docutils literal">from .os import sep</code>) fails. This

804

fixes a bug, but could possibly break certain <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal">import</code></a>

805

statements that were only working by accident. (Fixed by Meador Inge;

806

<a class="reference external" href="https://bugs.python.org/issue7902">issue 7902</a>.)

807

</li>

808

<li>It’s now possible for a subclass of the built-in <a class="reference internal" href="../library/functions.html#unicode" title="unicode"><code class="xref py py-class docutils literal">unicode</code></a> type

809

to override the <a class="reference internal" href="../reference/datamodel.html#object.__unicode__" title="object.__unicode__"><code class="xref py py-meth docutils literal">__unicode__()</code></a> method. (Implemented by

810

Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue1583863">issue 1583863</a>.)

811

</li>

812

<li>The <a class="reference internal" href="../library/functions.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal">bytearray</code></a> type’s <code class="xref py py-meth docutils literal">translate()</code> method now accepts

813

<code class="docutils literal">None</code> as its first argument. (Fixed by Georg Brandl;

814

<a class="reference external" href="https://bugs.python.org/issue4759">issue 4759</a>.)

815

</li>

816

<li>When using <code class="docutils literal">@classmethod</code> and <code class="docutils literal">@staticmethod</code> to wrap

817

methods as class or static methods, the wrapper object now

818

exposes the wrapped function as their <code class="xref py py-attr docutils literal">__func__</code> attribute.

819

(Contributed by Amaury Forgeot d’Arc, after a suggestion by

820

George Sakkis; <a class="reference external" href="https://bugs.python.org/issue5982">issue 5982</a>.)

821

</li>

822

<li>When a restricted set of attributes were set using <code class="docutils literal">__slots__</code>,

823

deleting an unset attribute would not raise <a class="reference internal" href="../library/exceptions.html#exceptions.AttributeError" title="exceptions.AttributeError"><code class="xref py py-exc docutils literal">AttributeError</code></a>

824

as you would expect. Fixed by Benjamin Peterson; <a class="reference external" href="https://bugs.python.org/issue7604">issue 7604</a>.)

825

</li>

826

<li>Two new encodings are now supported: “cp720”, used primarily for

827

Arabic text; and “cp858”, a variant of CP 850 that adds the euro

828

symbol. (CP720 contributed by Alexander Belchenko and Amaury

829

Forgeot d’Arc in <a class="reference external" href="https://bugs.python.org/issue1616979">issue 1616979</a>; CP858 contributed by Tim Hatch in

830

<a class="reference external" href="https://bugs.python.org/issue8016">issue 8016</a>.)

831

</li>

832

<li>The <a class="reference internal" href="../library/functions.html#file" title="file"><code class="xref py py-class docutils literal">file</code></a> object will now set the <code class="xref py py-attr docutils literal">filename</code> attribute

833

on the <a class="reference internal" href="../library/exceptions.html#exceptions.IOError" title="exceptions.IOError"><code class="xref py py-exc docutils literal">IOError</code></a> exception when trying to open a directory

834

on POSIX platforms (noted by Jan Kaliszewski; <a class="reference external" href="https://bugs.python.org/issue4764">issue 4764</a>), and

835

now explicitly checks for and forbids writing to read-only file objects

836

instead of trusting the C library to catch and report the error

837

(fixed by Stefan Krah; <a class="reference external" href="https://bugs.python.org/issue5677">issue 5677</a>).

838

</li>

839

<li>The Python tokenizer now translates line endings itself, so the

840

<a class="reference internal" href="../library/functions.html#compile" title="compile"><code class="xref py py-func docutils literal">compile()</code></a> built-in function now accepts code using any

841

line-ending convention. Additionally, it no longer requires that the

842

code end in a newline.

843

</li>

844

<li>Extra parentheses in function definitions are illegal in Python 3.x,

845

meaning that you get a syntax error from <code class="docutils literal">def f((x)): pass</code>. In

846

Python3-warning mode, Python 2.7 will now warn about this odd usage.

847

(Noted by James Lingard; <a class="reference external" href="https://bugs.python.org/issue7362">issue 7362</a>.)

848

</li>

849

<li>It’s now possible to create weak references to old-style class

850

objects. New-style classes were always weak-referenceable. (Fixed

851

by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue8268">issue 8268</a>.)

852

</li>

853

<li>When a module object is garbage-collected, the module’s dictionary is

854

now only cleared if no one else is holding a reference to the

855

dictionary (<a class="reference external" href="https://bugs.python.org/issue7140">issue 7140</a>).

856

</li>

857

</ul>

858

859

<h3>Interpreter Changes<a class="headerlink" href="#interpreter-changes" title="Permalink to this headline">¶</a></h3>

860

A new environment variable, <a class="reference internal" href="../using/cmdline.html#envvar-PYTHONWARNINGS"><code class="xref std std-envvar docutils literal">PYTHONWARNINGS</code></a>,

861

allows controlling warnings. It should be set to a string

862

containing warning settings, equivalent to those

863

used with the <a class="reference internal" href="../using/cmdline.html#cmdoption-W"><code class="xref std std-option docutils literal">-W</code></a> switch, separated by commas.

864

(Contributed by Brian Curtin; <a class="reference external" href="https://bugs.python.org/issue7301">issue 7301</a>.)

865

For example, the following setting will print warnings every time

866

they occur, but turn warnings from the <a class="reference internal" href="../library/cookie.html#module-Cookie" title="Cookie: Support for HTTP state management (cookies)."><code class="xref py py-mod docutils literal">Cookie</code></a> module into an

867

error. (The exact syntax for setting an environment variable varies

868

across operating systems and shells.)

869

<div class="highlight-python"><div class="highlight"><pre>export PYTHONWARNINGS=all,error:::Cookie:0

870

</pre></div>

871

</div>

872

</div>

873

874

<h3>Optimizations<a class="headerlink" href="#optimizations" title="Permalink to this headline">¶</a></h3>

875

Several performance enhancements have been added:

876

<ul>

877

<li>A new opcode was added to perform the initial setup for

878

<a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal">with</code></a> statements, looking up the <a class="reference internal" href="../reference/datamodel.html#object.__enter__" title="object.__enter__"><code class="xref py py-meth docutils literal">__enter__()</code></a> and

879

<a class="reference internal" href="../reference/datamodel.html#object.__exit__" title="object.__exit__"><code class="xref py py-meth docutils literal">__exit__()</code></a> methods. (Contributed by Benjamin Peterson.)

880

</li>

881

<li>The garbage collector now performs better for one common usage

882

pattern: when many objects are being allocated without deallocating

883

any of them. This would previously take quadratic

884

time for garbage collection, but now the number of full garbage collections

885

is reduced as the number of objects on the heap grows.

886

The new logic only performs a full garbage collection pass when

887

the middle generation has been collected 10 times and when the

888

number of survivor objects from the middle generation exceeds 10% of

889

the number of objects in the oldest generation. (Suggested by Martin

890

von Löwis and implemented by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue4074">issue 4074</a>.)

891

</li>

892

<li>The garbage collector tries to avoid tracking simple containers

893

which can’t be part of a cycle. In Python 2.7, this is now true for

894

tuples and dicts containing atomic types (such as ints, strings,

895

etc.). Transitively, a dict containing tuples of atomic types won’t

896

be tracked either. This helps reduce the cost of each

897

garbage collection by decreasing the number of objects to be

898

considered and traversed by the collector.

899

(Contributed by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue4688">issue 4688</a>.)

900

</li>

901

<li>Long integers are now stored internally either in base 2**15 or in base

902

2**30, the base being determined at build time. Previously, they

903

were always stored in base 2**15. Using base 2**30 gives

904

significant performance improvements on 64-bit machines, but

905

benchmark results on 32-bit machines have been mixed. Therefore,

906

the default is to use base 2**30 on 64-bit machines and base 2**15

907

on 32-bit machines; on Unix, there’s a new configure option

908

<code class="xref std std-option docutils literal">--enable-big-digits</code> that can be used to override this default.

909

Apart from the performance improvements this change should be

910

invisible to end users, with one exception: for testing and

911

debugging purposes there’s a new structseq <a class="reference internal" href="../library/sys.html#sys.long_info" title="sys.long_info"><code class="xref py py-data docutils literal">sys.long_info</code></a> that

912

provides information about the internal format, giving the number of

913

bits per digit and the size in bytes of the C type used to store

914

each digit:

915

<div class="highlight-python"><div class="highlight"><pre>>>> import sys

916

>>> sys.long_info

917

sys.long_info(bits_per_digit=30, sizeof_digit=4)

918

</pre></div>

919

</div>

920

(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue4258">issue 4258</a>.)

921

Another set of changes made long objects a few bytes smaller: 2 bytes

922

smaller on 32-bit systems and 6 bytes on 64-bit.

923

(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue5260">issue 5260</a>.)

924

</li>

925

<li>The division algorithm for long integers has been made faster

926

by tightening the inner loop, doing shifts instead of multiplications,

927

and fixing an unnecessary extra iteration.

928

Various benchmarks show speedups of between 50% and 150% for long

929

integer divisions and modulo operations.

930

(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue5512">issue 5512</a>.)

931

Bitwise operations are also significantly faster (initial patch by

932

Gregory Smith; <a class="reference external" href="https://bugs.python.org/issue1087418">issue 1087418</a>).

933

</li>

934

<li>The implementation of <code class="docutils literal">%</code> checks for the left-side operand being

935

a Python string and special-cases it; this results in a 1-3%

936

performance increase for applications that frequently use <code class="docutils literal">%</code>

937

with strings, such as templating libraries.

938

(Implemented by Collin Winter; <a class="reference external" href="https://bugs.python.org/issue5176">issue 5176</a>.)

939

</li>

940

<li>List comprehensions with an <code class="docutils literal">if</code> condition are compiled into

941

faster bytecode. (Patch by Antoine Pitrou, back-ported to 2.7

942

by Jeffrey Yasskin; <a class="reference external" href="https://bugs.python.org/issue4715">issue 4715</a>.)

943

</li>

944

<li>Converting an integer or long integer to a decimal string was made

945

faster by special-casing base 10 instead of using a generalized

946

conversion function that supports arbitrary bases.

947

(Patch by Gawain Bolton; <a class="reference external" href="https://bugs.python.org/issue6713">issue 6713</a>.)

948

</li>

949

<li>The <code class="xref py py-meth docutils literal">split()</code>, <code class="xref py py-meth docutils literal">replace()</code>, <code class="xref py py-meth docutils literal">rindex()</code>,

950

<code class="xref py py-meth docutils literal">rpartition()</code>, and <code class="xref py py-meth docutils literal">rsplit()</code> methods of string-like types

951

(strings, Unicode strings, and <a class="reference internal" href="../library/functions.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal">bytearray</code></a> objects) now use a

952

fast reverse-search algorithm instead of a character-by-character

953

scan. This is sometimes faster by a factor of 10. (Added by

954

Florent Xicluna; <a class="reference external" href="https://bugs.python.org/issue7462">issue 7462</a> and <a class="reference external" href="https://bugs.python.org/issue7622">issue 7622</a>.)

955

</li>

956

<li>The <a class="reference internal" href="../library/pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal">pickle</code></a> and <a class="reference internal" href="../library/pickle.html#module-cPickle" title="cPickle: Faster version of pickle, but not subclassable."><code class="xref py py-mod docutils literal">cPickle</code></a> modules now automatically

957

intern the strings used for attribute names, reducing memory usage

958

of the objects resulting from unpickling. (Contributed by Jake

959

McGuire; <a class="reference external" href="https://bugs.python.org/issue5084">issue 5084</a>.)

960

</li>

961

<li>The <a class="reference internal" href="../library/pickle.html#module-cPickle" title="cPickle: Faster version of pickle, but not subclassable."><code class="xref py py-mod docutils literal">cPickle</code></a> module now special-cases dictionaries,

962

nearly halving the time required to pickle them.

963

(Contributed by Collin Winter; <a class="reference external" href="https://bugs.python.org/issue5670">issue 5670</a>.)

964

</li>

965

</ul>

966

</div>

967

</div>

968

969

<h2>New and Improved Modules<a class="headerlink" href="#new-and-improved-modules" title="Permalink to this headline">¶</a></h2>

970

As in every release, Python’s standard library received a number of

971

enhancements and bug fixes. Here’s a partial list of the most notable

972

changes, sorted alphabetically by module name. Consult the

973

<code class="file docutils literal">Misc/NEWS</code> file in the source tree for a more complete list of

974

changes, or look through the Subversion logs for all the details.

975

<ul>

976

<li>The <a class="reference internal" href="../library/bdb.html#module-bdb" title="bdb: Debugger framework."><code class="xref py py-mod docutils literal">bdb</code></a> module’s base debugging class <a class="reference internal" href="../library/bdb.html#bdb.Bdb" title="bdb.Bdb"><code class="xref py py-class docutils literal">Bdb</code></a>

977

gained a feature for skipping modules. The constructor

978

now takes an iterable containing glob-style patterns such as

979

<code class="docutils literal">django.*</code>; the debugger will not step into stack frames

980

from a module that matches one of these patterns.

981

(Contributed by Maru Newby after a suggestion by

982

Senthil Kumaran; <a class="reference external" href="https://bugs.python.org/issue5142">issue 5142</a>.)

983

</li>

984

<li>The <a class="reference internal" href="../library/binascii.html#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal">binascii</code></a> module now supports the buffer API, so it can be

985

used with <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal">memoryview</code></a> instances and other similar buffer objects.

986

(Backported from 3.x by Florent Xicluna; <a class="reference external" href="https://bugs.python.org/issue7703">issue 7703</a>.)

987

</li>

988

<li>Updated module: the <a class="reference internal" href="../library/bsddb.html#module-bsddb" title="bsddb: Interface to Berkeley DB database library"><code class="xref py py-mod docutils literal">bsddb</code></a> module has been updated from 4.7.2devel9

989

to version 4.8.4 of

990

<a class="reference external" href="http://www.jcea.es/programacion/pybsddb.htm">the pybsddb package</a>.

991

The new version features better Python 3.x compatibility, various bug fixes,

992

and adds several new BerkeleyDB flags and methods.

993

(Updated by Jesús Cea Avión; <a class="reference external" href="https://bugs.python.org/issue8156">issue 8156</a>. The pybsddb

994

changelog can be read at <a class="reference external" href="http://hg.jcea.es/pybsddb/file/tip/ChangeLog">http://hg.jcea.es/pybsddb/file/tip/ChangeLog</a>.)

995

</li>

996

<li>The <a class="reference internal" href="../library/bz2.html#module-bz2" title="bz2: Interface to compression and decompression routines compatible with bzip2."><code class="xref py py-mod docutils literal">bz2</code></a> module’s <a class="reference internal" href="../library/bz2.html#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal">BZ2File</code></a> now supports the context

997

management protocol, so you can write <code class="docutils literal">with bz2.BZ2File(...) as f:</code>.

998

(Contributed by Hagen Fürstenau; <a class="reference external" href="https://bugs.python.org/issue3860">issue 3860</a>.)

999

</li>

1000

<li>New class: the <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal">Counter</code></a> class in the <a class="reference internal" href="../library/collections.html#module-collections" title="collections: High-performance datatypes"><code class="xref py py-mod docutils literal">collections</code></a>

1001

module is useful for tallying data. <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal">Counter</code></a> instances

1002

behave mostly like dictionaries but return zero for missing keys instead of

1003

raising a <a class="reference internal" href="../library/exceptions.html#exceptions.KeyError" title="exceptions.KeyError"><code class="xref py py-exc docutils literal">KeyError</code></a>:

1004

1005

>>> c = Counter()

1006

>>> for letter in 'here is a sample of english text':

1007

... c[letter] += 1

1008

...

1009

>>> c

1010

Counter({' ': 6, 'e': 5, 's': 3, 'a': 2, 'i': 2, 'h': 2,

1011

'l': 2, 't': 2, 'g': 1, 'f': 1, 'm': 1, 'o': 1, 'n': 1,

1012

'p': 1, 'r': 1, 'x': 1})

1013

>>> c['e']

1014

5

1015

>>> c['z']

1016

0

1017

</pre></div>

1018

</div>

1019

There are three additional <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal">Counter</code></a> methods.

1020

<a class="reference internal" href="../library/collections.html#collections.Counter.most_common" title="collections.Counter.most_common"><code class="xref py py-meth docutils literal">most_common()</code></a> returns the N most common

1021

elements and their counts. <a class="reference internal" href="../library/collections.html#collections.Counter.elements" title="collections.Counter.elements"><code class="xref py py-meth docutils literal">elements()</code></a>

1022

returns an iterator over the contained elements, repeating each

1023

element as many times as its count.

1024

<a class="reference internal" href="../library/collections.html#collections.Counter.subtract" title="collections.Counter.subtract"><code class="xref py py-meth docutils literal">subtract()</code></a> takes an iterable and

1025

subtracts one for each element instead of adding; if the argument is

1026

a dictionary or another <code class="xref py py-class docutils literal">Counter</code>, the counts are

1027

subtracted.

1028

<div class="highlight-python"><div class="highlight"><pre>>>> c.most_common(5)

1029

[(' ', 6), ('e', 5), ('s', 3), ('a', 2), ('i', 2)]

1030

>>> c.elements() ->

1031

'a', 'a', ' ', ' ', ' ', ' ', ' ', ' ',

1032

'e', 'e', 'e', 'e', 'e', 'g', 'f', 'i', 'i',

1033

'h', 'h', 'm', 'l', 'l', 'o', 'n', 'p', 's',

1034

's', 's', 'r', 't', 't', 'x'

1035

>>> c['e']

1036

5

1037

>>> c.subtract('very heavy on the letter e')

1038

>>> c['e'] # Count is now lower

1039

-1

1040

</pre></div>

1041

</div>

1042

Contributed by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue1696199">issue 1696199</a>.

1043

New class: <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal">OrderedDict</code></a> is described in the earlier

1044

section <a class="reference internal" href="#pep-0372">PEP 372: Adding an Ordered Dictionary to collections</a>.

1045

New method: The <a class="reference internal" href="../library/collections.html#collections.deque" title="collections.deque"><code class="xref py py-class docutils literal">deque</code></a> data type now has a

1046

<a class="reference internal" href="../library/collections.html#collections.deque.count" title="collections.deque.count"><code class="xref py py-meth docutils literal">count()</code></a> method that returns the number of

1047

contained elements equal to the supplied argument x, and a

1048

<a class="reference internal" href="../library/collections.html#collections.deque.reverse" title="collections.deque.reverse"><code class="xref py py-meth docutils literal">reverse()</code></a> method that reverses the elements

1049

of the deque in-place. <a class="reference internal" href="../library/collections.html#collections.deque" title="collections.deque"><code class="xref py py-class docutils literal">deque</code></a> also exposes its maximum

1050

length as the read-only <a class="reference internal" href="../library/collections.html#collections.deque.maxlen" title="collections.deque.maxlen"><code class="xref py py-attr docutils literal">maxlen</code></a> attribute.

1051

(Both features added by Raymond Hettinger.)

1052

The <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-class docutils literal">namedtuple</code></a> class now has an optional rename parameter.

1053

If rename is true, field names that are invalid because they’ve

1054

been repeated or aren’t legal Python identifiers will be

1055

renamed to legal names that are derived from the field’s

1056

position within the list of fields:

1057

1058

>>> T = namedtuple('T', ['field1', '$illegal', 'for', 'field2'], rename=True)

1059

>>> T._fields

1060

('field1', '_1', '_2', 'field2')

1061

</pre></div>

1062

</div>

1063

(Added by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue1818">issue 1818</a>.)

1064

Finally, the <a class="reference internal" href="../library/collections.html#collections.Mapping" title="collections.Mapping"><code class="xref py py-class docutils literal">Mapping</code></a> abstract base class now

1065

returns <a class="reference internal" href="../library/constants.html#NotImplemented" title="NotImplemented"><code class="xref py py-const docutils literal">NotImplemented</code></a> if a mapping is compared to

1066

another type that isn’t a <code class="xref py py-class docutils literal">Mapping</code>.

1067

(Fixed by Daniel Stutzbach; <a class="reference external" href="https://bugs.python.org/issue8729">issue 8729</a>.)

1068

</li>

1069

<li>Constructors for the parsing classes in the <a class="reference internal" href="../library/configparser.html#module-ConfigParser" title="ConfigParser: Configuration file parser."><code class="xref py py-mod docutils literal">ConfigParser</code></a> module now

1070

take an allow_no_value parameter, defaulting to false; if true,

1071

options without values will be allowed. For example:

1072

<div class="highlight-python"><div class="highlight"><pre>>>> import ConfigParser, StringIO

1073

>>> sample_config = """

1074

... [mysqld]

1075

... user = mysql

1076

... pid-file = /var/run/mysqld/mysqld.pid

1077

... skip-bdb

1078

... """

1079

>>> config = ConfigParser.RawConfigParser(allow_no_value=True)

1080

>>> config.readfp(StringIO.StringIO(sample_config))

1081

>>> config.get('mysqld', 'user')

1082

'mysql'

1083

>>> print config.get('mysqld', 'skip-bdb')

1084

None

1085

1086

Traceback (most recent call last):

1087

...

1088

NoOptionError: No option 'unknown' in section: 'mysqld'

1089

</pre></div>

1090

</div>

1091

(Contributed by Mats Kindahl; <a class="reference external" href="https://bugs.python.org/issue7005">issue 7005</a>.)

1092

</li>

1093

<li>Deprecated function: <a class="reference internal" href="../library/contextlib.html#contextlib.nested" title="contextlib.nested"><code class="xref py py-func docutils literal">contextlib.nested()</code></a>, which allows

1094

handling more than one context manager with a single <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal">with</code></a>

1095

statement, has been deprecated, because the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal">with</code></a> statement

1096

now supports multiple context managers.

1097

</li>

1098

<li>The <a class="reference internal" href="../library/cookielib.html#module-cookielib" title="cookielib: Classes for automatic handling of HTTP cookies."><code class="xref py py-mod docutils literal">cookielib</code></a> module now ignores cookies that have an invalid

1099

version field, one that doesn’t contain an integer value. (Fixed by

1100

John J. Lee; <a class="reference external" href="https://bugs.python.org/issue3924">issue 3924</a>.)

1101

</li>

1102

<li>The <a class="reference internal" href="../library/copy.html#module-copy" title="copy: Shallow and deep copy operations."><code class="xref py py-mod docutils literal">copy</code></a> module’s <a class="reference internal" href="../library/copy.html#copy.deepcopy" title="copy.deepcopy"><code class="xref py py-func docutils literal">deepcopy()</code></a> function will now

1103

correctly copy bound instance methods. (Implemented by

1104

Robert Collins; <a class="reference external" href="https://bugs.python.org/issue1515">issue 1515</a>.)

1105

</li>

1106

<li>The <a class="reference internal" href="../library/ctypes.html#module-ctypes" title="ctypes: A foreign function library for Python."><code class="xref py py-mod docutils literal">ctypes</code></a> module now always converts <code class="docutils literal">None</code> to a C NULL

1107

pointer for arguments declared as pointers. (Changed by Thomas

1108

Heller; <a class="reference external" href="https://bugs.python.org/issue4606">issue 4606</a>.) The underlying <a class="reference external" href="http://sourceware.org/libffi/">libffi library</a> has been updated to version

1109

3.0.9, containing various fixes for different platforms. (Updated

1110

by Matthias Klose; <a class="reference external" href="https://bugs.python.org/issue8142">issue 8142</a>.)

1111

</li>

1112

<li>New method: the <a class="reference internal" href="../library/datetime.html#module-datetime" title="datetime: Basic date and time types."><code class="xref py py-mod docutils literal">datetime</code></a> module’s <a class="reference internal" href="../library/datetime.html#datetime.timedelta" title="datetime.timedelta"><code class="xref py py-class docutils literal">timedelta</code></a> class

1113

gained a <a class="reference internal" href="../library/datetime.html#datetime.timedelta.total_seconds" title="datetime.timedelta.total_seconds"><code class="xref py py-meth docutils literal">total_seconds()</code></a> method that returns the

1114

number of seconds in the duration. (Contributed by Brian Quinlan; <a class="reference external" href="https://bugs.python.org/issue5788">issue 5788</a>.)

1115

</li>

1116

<li>New method: the <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a> class gained a

1117

<a class="reference internal" href="../library/decimal.html#decimal.Decimal.from_float" title="decimal.Decimal.from_float"><code class="xref py py-meth docutils literal">from_float()</code></a> class method that performs an exact

1118

conversion of a floating-point number to a <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a>.

1119

This exact conversion strives for the

1120

closest decimal approximation to the floating-point representation’s value;

1121

the resulting decimal value will therefore still include the inaccuracy,

1122

if any.

1123

For example, <code class="docutils literal">Decimal.from_float(0.1)</code> returns

1124

<code class="docutils literal">Decimal('0.1000000000000000055511151231257827021181583404541015625')</code>.

1125

(Implemented by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue4796">issue 4796</a>.)

1126

Comparing instances of <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a> with floating-point

1127

numbers now produces sensible results based on the numeric values

1128

of the operands. Previously such comparisons would fall back to

1129

Python’s default rules for comparing objects, which produced arbitrary

1130

results based on their type. Note that you still cannot combine

1131

<code class="xref py py-class docutils literal">Decimal</code> and floating-point in other operations such as addition,

1132

since you should be explicitly choosing how to convert between float and

1133

<a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a>. (Fixed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue2531">issue 2531</a>.)

1134

The constructor for <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a> now accepts

1135

floating-point numbers (added by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue8257">issue 8257</a>)

1136

and non-European Unicode characters such as Arabic-Indic digits

1137

(contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue6595">issue 6595</a>).

1138

Most of the methods of the <a class="reference internal" href="../library/decimal.html#decimal.Context" title="decimal.Context"><code class="xref py py-class docutils literal">Context</code></a> class now accept integers

1139

as well as <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a> instances; the only exceptions are the

1140

<a class="reference internal" href="../library/decimal.html#decimal.Context.canonical" title="decimal.Context.canonical"><code class="xref py py-meth docutils literal">canonical()</code></a> and <a class="reference internal" href="../library/decimal.html#decimal.Context.is_canonical" title="decimal.Context.is_canonical"><code class="xref py py-meth docutils literal">is_canonical()</code></a>

1141

methods. (Patch by Juan José Conti; <a class="reference external" href="https://bugs.python.org/issue7633">issue 7633</a>.)

1142

When using <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a> instances with a string’s

1143

<a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal">format()</code></a> method, the default alignment was previously

1144

left-alignment. This has been changed to right-alignment, which is

1145

more sensible for numeric types. (Changed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue6857">issue 6857</a>.)

1146

Comparisons involving a signaling NaN value (or <code class="docutils literal">sNAN</code>) now signal

1147

<code class="xref py py-const docutils literal">InvalidOperation</code> instead of silently returning a true or

1148

false value depending on the comparison operator. Quiet NaN values

1149

(or <code class="docutils literal">NaN</code>) are now hashable. (Fixed by Mark Dickinson;

1150

<a class="reference external" href="https://bugs.python.org/issue7279">issue 7279</a>.)

1151

</li>

1152

<li>The <a class="reference internal" href="../library/difflib.html#module-difflib" title="difflib: Helpers for computing differences between objects."><code class="xref py py-mod docutils literal">difflib</code></a> module now produces output that is more

1153

compatible with modern diff/patch tools

1154

through one small change, using a tab character instead of spaces as

1155

a separator in the header giving the filename. (Fixed by Anatoly

1156

Techtonik; <a class="reference external" href="https://bugs.python.org/issue7585">issue 7585</a>.)

1157

</li>

1158

<li>The Distutils <code class="docutils literal">sdist</code> command now always regenerates the

1159

<code class="file docutils literal">MANIFEST</code> file, since even if the <code class="file docutils literal">MANIFEST.in</code> or

1160

<code class="file docutils literal">setup.py</code> files haven’t been modified, the user might have

1161

created some new files that should be included.

1162

(Fixed by Tarek Ziadé; <a class="reference external" href="https://bugs.python.org/issue8688">issue 8688</a>.)

1163

</li>

1164

<li>The <a class="reference internal" href="../library/doctest.html#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal">doctest</code></a> module’s <code class="xref py py-const docutils literal">IGNORE_EXCEPTION_DETAIL</code> flag

1165

will now ignore the name of the module containing the exception

1166

being tested. (Patch by Lennart Regebro; <a class="reference external" href="https://bugs.python.org/issue7490">issue 7490</a>.)

1167

</li>

1168

<li>The <a class="reference internal" href="../library/email.html#module-email" title="email: Package supporting the parsing, manipulating, and generating email messages, including MIME documents."><code class="xref py py-mod docutils literal">email</code></a> module’s <a class="reference internal" href="../library/email.message.html#email.message.Message" title="email.message.Message"><code class="xref py py-class docutils literal">Message</code></a> class will

1169

now accept a Unicode-valued payload, automatically converting the

1170

payload to the encoding specified by <code class="xref py py-attr docutils literal">output_charset</code>.

1171

(Added by R. David Murray; <a class="reference external" href="https://bugs.python.org/issue1368247">issue 1368247</a>.)

1172

</li>

1173

<li>The <a class="reference internal" href="../library/fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal">Fraction</code></a> class now accepts a single float or

1174

1175

arguments to its constructor. (Implemented by Mark Dickinson;

1176

rationals added in <a class="reference external" href="https://bugs.python.org/issue5812">issue 5812</a>, and float/decimal in

1177

<a class="reference external" href="https://bugs.python.org/issue8294">issue 8294</a>.)

1178

Ordering comparisons (<code class="docutils literal"><</code>, <code class="docutils literal"><=</code>, <code class="docutils literal">></code>, <code class="docutils literal">>=</code>) between

1179

fractions and complex numbers now raise a <a class="reference internal" href="../library/exceptions.html#exceptions.TypeError" title="exceptions.TypeError"><code class="xref py py-exc docutils literal">TypeError</code></a>.

1180

This fixes an oversight, making the <a class="reference internal" href="../library/fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal">Fraction</code></a>

1181

match the other numeric types.

1182

</li>

1183

<li>New class: <a class="reference internal" href="../library/ftplib.html#ftplib.FTP_TLS" title="ftplib.FTP_TLS"><code class="xref py py-class docutils literal">FTP_TLS</code></a> in

1184

the <a class="reference internal" href="../library/ftplib.html#module-ftplib" title="ftplib: FTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal">ftplib</code></a> module provides secure FTP

1185

connections using TLS encapsulation of authentication as well as

1186

subsequent control and data transfers.

1187

(Contributed by Giampaolo Rodola; <a class="reference external" href="https://bugs.python.org/issue2054">issue 2054</a>.)

1188

The <a class="reference internal" href="../library/ftplib.html#ftplib.FTP.storbinary" title="ftplib.FTP.storbinary"><code class="xref py py-meth docutils literal">storbinary()</code></a> method for binary uploads can now restart

1189

uploads thanks to an added rest parameter (patch by Pablo Mouzo;

1190

<a class="reference external" href="https://bugs.python.org/issue6845">issue 6845</a>.)

1191

</li>

1192

<li>New class decorator: <a class="reference internal" href="../library/functools.html#functools.total_ordering" title="functools.total_ordering"><code class="xref py py-func docutils literal">total_ordering()</code></a> in the <a class="reference internal" href="../library/functools.html#module-functools" title="functools: Higher-order functions and operations on callable objects."><code class="xref py py-mod docutils literal">functools</code></a>

1193

module takes a class that defines an <a class="reference internal" href="../reference/datamodel.html#object.__eq__" title="object.__eq__"><code class="xref py py-meth docutils literal">__eq__()</code></a> method and one of

1194

<a class="reference internal" href="../reference/datamodel.html#object.__lt__" title="object.__lt__"><code class="xref py py-meth docutils literal">__lt__()</code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__le__" title="object.__le__"><code class="xref py py-meth docutils literal">__le__()</code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__gt__" title="object.__gt__"><code class="xref py py-meth docutils literal">__gt__()</code></a>, or <a class="reference internal" href="../reference/datamodel.html#object.__ge__" title="object.__ge__"><code class="xref py py-meth docutils literal">__ge__()</code></a>,

1195

and generates the missing comparison methods. Since the

1196

<a class="reference internal" href="../reference/datamodel.html#object.__cmp__" title="object.__cmp__"><code class="xref py py-meth docutils literal">__cmp__()</code></a> method is being deprecated in Python 3.x,

1197

this decorator makes it easier to define ordered classes.

1198

(Added by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue5479">issue 5479</a>.)

1199

New function: <a class="reference internal" href="../library/functools.html#functools.cmp_to_key" title="functools.cmp_to_key"><code class="xref py py-func docutils literal">cmp_to_key()</code></a> will take an old-style comparison

1200

function that expects two arguments and return a new callable that

1201

can be used as the key parameter to functions such as

1202

<a class="reference internal" href="../library/functions.html#sorted" title="sorted"><code class="xref py py-func docutils literal">sorted()</code></a>, <a class="reference internal" href="../library/functions.html#min" title="min"><code class="xref py py-func docutils literal">min()</code></a> and <a class="reference internal" href="../library/functions.html#max" title="max"><code class="xref py py-func docutils literal">max()</code></a>, etc. The primary

1203

intended use is to help with making code compatible with Python 3.x.

1204

(Added by Raymond Hettinger.)

1205

</li>

1206

<li>New function: the <a class="reference internal" href="../library/gc.html#module-gc" title="gc: Interface to the cycle-detecting garbage collector."><code class="xref py py-mod docutils literal">gc</code></a> module’s <a class="reference internal" href="../library/gc.html#gc.is_tracked" title="gc.is_tracked"><code class="xref py py-func docutils literal">is_tracked()</code></a> returns

1207

true if a given instance is tracked by the garbage collector, false

1208

otherwise. (Contributed by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue4688">issue 4688</a>.)

1209

</li>

1210

<li>The <a class="reference internal" href="../library/gzip.html#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><code class="xref py py-mod docutils literal">gzip</code></a> module’s <a class="reference internal" href="../library/gzip.html#gzip.GzipFile" title="gzip.GzipFile"><code class="xref py py-class docutils literal">GzipFile</code></a> now supports the context

1211

management protocol, so you can write <code class="docutils literal">with gzip.GzipFile(...) as f:</code>

1212

(contributed by Hagen Fürstenau; <a class="reference external" href="https://bugs.python.org/issue3860">issue 3860</a>), and it now implements

1213

the <a class="reference internal" href="../library/io.html#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal">io.BufferedIOBase</code></a> ABC, so you can wrap it with

1214

<a class="reference internal" href="../library/io.html#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal">io.BufferedReader</code></a> for faster processing

1215

(contributed by Nir Aides; <a class="reference external" href="https://bugs.python.org/issue7471">issue 7471</a>).

1216

It’s also now possible to override the modification time

1217

recorded in a gzipped file by providing an optional timestamp to

1218

the constructor. (Contributed by Jacques Frechet; <a class="reference external" href="https://bugs.python.org/issue4272">issue 4272</a>.)

1219

Files in gzip format can be padded with trailing zero bytes; the

1220

<a class="reference internal" href="../library/gzip.html#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><code class="xref py py-mod docutils literal">gzip</code></a> module will now consume these trailing bytes. (Fixed by

1221

Tadek Pietraszek and Brian Curtin; <a class="reference external" href="https://bugs.python.org/issue2846">issue 2846</a>.)

1222

</li>

1223

<li>New attribute: the <a class="reference internal" href="../library/hashlib.html#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code class="xref py py-mod docutils literal">hashlib</code></a> module now has an <a class="reference internal" href="../library/hashlib.html#hashlib.hashlib.algorithms" title="hashlib.hashlib.algorithms"><code class="xref py py-attr docutils literal">algorithms</code></a>

1224

attribute containing a tuple naming the supported algorithms.

1225

In Python 2.7, <code class="docutils literal">hashlib.algorithms</code> contains

1226

<code class="docutils literal">('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512')</code>.

1227

(Contributed by Carl Chenet; <a class="reference external" href="https://bugs.python.org/issue7418">issue 7418</a>.)

1228

</li>

1229

<li>The default <a class="reference internal" href="../library/httplib.html#httplib.HTTPResponse" title="httplib.HTTPResponse"><code class="xref py py-class docutils literal">HTTPResponse</code></a> class used by the <a class="reference internal" href="../library/httplib.html#module-httplib" title="httplib: HTTP and HTTPS protocol client (requires sockets)."><code class="xref py py-mod docutils literal">httplib</code></a> module now

1230

supports buffering, resulting in much faster reading of HTTP responses.

1231

(Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue4879">issue 4879</a>.)

1232

The <a class="reference internal" href="../library/httplib.html#httplib.HTTPConnection" title="httplib.HTTPConnection"><code class="xref py py-class docutils literal">HTTPConnection</code></a> and <a class="reference internal" href="../library/httplib.html#httplib.HTTPSConnection" title="httplib.HTTPSConnection"><code class="xref py py-class docutils literal">HTTPSConnection</code></a> classes

1233

now support a source_address parameter, a <code class="docutils literal">(host, port)</code> 2-tuple

1234

giving the source address that will be used for the connection.

1235

(Contributed by Eldon Ziegler; <a class="reference external" href="https://bugs.python.org/issue3972">issue 3972</a>.)

1236

</li>

1237

<li>The <code class="xref py py-mod docutils literal">ihooks</code> module now supports relative imports. Note that

1238

<code class="xref py py-mod docutils literal">ihooks</code> is an older module for customizing imports,

1239

superseded by the <a class="reference internal" href="../library/imputil.html#module-imputil" title="imputil: Manage and augment the import process. (deprecated)"><code class="xref py py-mod docutils literal">imputil</code></a> module added in Python 2.0.

1240

(Relative import support added by Neil Schemenauer.)

1241

</li>

1242

<li>The <a class="reference internal" href="../library/imaplib.html#module-imaplib" title="imaplib: IMAP4 protocol client (requires sockets)."><code class="xref py py-mod docutils literal">imaplib</code></a> module now supports IPv6 addresses.

1243

(Contributed by Derek Morr; <a class="reference external" href="https://bugs.python.org/issue1655">issue 1655</a>.)

1244

</li>

1245

<li>New function: the <a class="reference internal" href="../library/inspect.html#module-inspect" title="inspect: Extract information and source code from live objects."><code class="xref py py-mod docutils literal">inspect</code></a> module’s <a class="reference internal" href="../library/inspect.html#inspect.getcallargs" title="inspect.getcallargs"><code class="xref py py-func docutils literal">getcallargs()</code></a>

1246

takes a callable and its positional and keyword arguments,

1247

and figures out which of the callable’s parameters will receive each argument,

1248

returning a dictionary mapping argument names to their values. For example:

1249

<div class="highlight-python"><div class="highlight"><pre>>>> from inspect import getcallargs

1250

>>> def f(a, b=1, *pos, **named):

1251

... pass

1252

>>> getcallargs(f, 1, 2, 3)

1253

{'a': 1, 'b': 2, 'pos': (3,), 'named': {}}

1254

>>> getcallargs(f, a=2, x=4)

1255

{'a': 2, 'b': 1, 'pos': (), 'named': {'x': 4}}

1256

>>> getcallargs(f)

1257

Traceback (most recent call last):

1258

...

1259

TypeError: f() takes at least 1 argument (0 given)

1260

</pre></div>

1261

</div>

1262

Contributed by George Sakkis; <a class="reference external" href="https://bugs.python.org/issue3135">issue 3135</a>.

1263

</li>

1264

<li>Updated module: The <a class="reference internal" href="../library/io.html#module-io" title="io: Core tools for working with streams."><code class="xref py py-mod docutils literal">io</code></a> library has been upgraded to the version shipped with

1265

Python 3.1. For 3.1, the I/O library was entirely rewritten in C

1266

and is 2 to 20 times faster depending on the task being performed. The

1267

original Python version was renamed to the <code class="xref py py-mod docutils literal">_pyio</code> module.

1268

One minor resulting change: the <a class="reference internal" href="../library/io.html#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal">io.TextIOBase</code></a> class now

1269

has an <code class="xref py py-attr docutils literal">errors</code> attribute giving the error setting

1270

used for encoding and decoding errors (one of <code class="docutils literal">'strict'</code>, <code class="docutils literal">'replace'</code>,

1271

<code class="docutils literal">'ignore'</code>).

1272

The <a class="reference internal" href="../library/io.html#io.FileIO" title="io.FileIO"><code class="xref py py-class docutils literal">io.FileIO</code></a> class now raises an <a class="reference internal" href="../library/exceptions.html#exceptions.OSError" title="exceptions.OSError"><code class="xref py py-exc docutils literal">OSError</code></a> when passed

1273

an invalid file descriptor. (Implemented by Benjamin Peterson;

1274

<a class="reference external" href="https://bugs.python.org/issue4991">issue 4991</a>.) The <a class="reference internal" href="../library/io.html#io.IOBase.truncate" title="io.IOBase.truncate"><code class="xref py py-meth docutils literal">truncate()</code></a> method now preserves the

1275

file position; previously it would change the file position to the

1276

end of the new file. (Fixed by Pascal Chambon; <a class="reference external" href="https://bugs.python.org/issue6939">issue 6939</a>.)

1277

</li>

1278

<li>New function: <code class="docutils literal">itertools.compress(data, selectors)</code> takes two

1279

iterators. Elements of data are returned if the corresponding

1280

value in selectors is true:

1281

<div class="highlight-python"><div class="highlight"><pre>itertools.compress('ABCDEF', [1,0,1,0,1,1]) =>

1282

A, C, E, F

1283

</pre></div>

1284

</div>

1285

New function: <code class="docutils literal">itertools.combinations_with_replacement(iter, r)</code>

1286

returns all the possible r-length combinations of elements from the

1287

iterable iter. Unlike <a class="reference internal" href="../library/itertools.html#itertools.combinations" title="itertools.combinations"><code class="xref py py-func docutils literal">combinations()</code></a>, individual elements

1288

can be repeated in the generated combinations:

1289

<div class="highlight-python"><div class="highlight"><pre>itertools.combinations_with_replacement('abc', 2) =>

1290

('a', 'a'), ('a', 'b'), ('a', 'c'),

1291

('b', 'b'), ('b', 'c'), ('c', 'c')

1292

</pre></div>

1293

</div>

1294

Note that elements are treated as unique depending on their position

1295

in the input, not their actual values.

1296

The <a class="reference internal" href="../library/itertools.html#itertools.count" title="itertools.count"><code class="xref py py-func docutils literal">itertools.count()</code></a> function now has a step argument that

1297

allows incrementing by values other than 1. <a class="reference internal" href="../library/itertools.html#itertools.count" title="itertools.count"><code class="xref py py-func docutils literal">count()</code></a> also

1298

now allows keyword arguments, and using non-integer values such as

1299

floats or <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a> instances. (Implemented by Raymond

1300

Hettinger; <a class="reference external" href="https://bugs.python.org/issue5032">issue 5032</a>.)

1301

<a class="reference internal" href="../library/itertools.html#itertools.combinations" title="itertools.combinations"><code class="xref py py-func docutils literal">itertools.combinations()</code></a> and <a class="reference internal" href="../library/itertools.html#itertools.product" title="itertools.product"><code class="xref py py-func docutils literal">itertools.product()</code></a>

1302

previously raised <a class="reference internal" href="../library/exceptions.html#exceptions.ValueError" title="exceptions.ValueError"><code class="xref py py-exc docutils literal">ValueError</code></a> for values of r larger than

1303

the input iterable. This was deemed a specification error, so they

1304

now return an empty iterator. (Fixed by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue4816">issue 4816</a>.)

1305

</li>

1306

<li>Updated module: The <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal">json</code></a> module was upgraded to version 2.0.9 of the

1307

simplejson package, which includes a C extension that makes

1308

encoding and decoding faster.

1309

(Contributed by Bob Ippolito; <a class="reference external" href="https://bugs.python.org/issue4136">issue 4136</a>.)

1310

To support the new <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal">collections.OrderedDict</code></a> type, <a class="reference internal" href="../library/json.html#json.load" title="json.load"><code class="xref py py-func docutils literal">json.load()</code></a>

1311

now has an optional object_pairs_hook parameter that will be called

1312

with any object literal that decodes to a list of pairs.

1313

(Contributed by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue5381">issue 5381</a>.)

1314

</li>

1315

<li>The <a class="reference internal" href="../library/mailbox.html#module-mailbox" title="mailbox: Manipulate mailboxes in various formats"><code class="xref py py-mod docutils literal">mailbox</code></a> module’s <a class="reference internal" href="../library/mailbox.html#mailbox.Maildir" title="mailbox.Maildir"><code class="xref py py-class docutils literal">Maildir</code></a> class now records the

1316

timestamp on the directories it reads, and only re-reads them if the

1317

modification time has subsequently changed. This improves

1318

performance by avoiding unneeded directory scans. (Fixed by

1319

A.M. Kuchling and Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue1607951">issue 1607951</a>, <a class="reference external" href="https://bugs.python.org/issue6896">issue 6896</a>.)

1320

</li>

1321

<li>New functions: the <a class="reference internal" href="../library/math.html#module-math" title="math: Mathematical functions (sin() etc.)."><code class="xref py py-mod docutils literal">math</code></a> module gained

1322

<a class="reference internal" href="../library/math.html#math.erf" title="math.erf"><code class="xref py py-func docutils literal">erf()</code></a> and <a class="reference internal" href="../library/math.html#math.erfc" title="math.erfc"><code class="xref py py-func docutils literal">erfc()</code></a> for the error function and the complementary error function,

1323

<a class="reference internal" href="../library/math.html#math.expm1" title="math.expm1"><code class="xref py py-func docutils literal">expm1()</code></a> which computes <code class="docutils literal">e**x - 1</code> with more precision than

1324

using <a class="reference internal" href="../library/math.html#math.exp" title="math.exp"><code class="xref py py-func docutils literal">exp()</code></a> and subtracting 1,

1325

<a class="reference internal" href="../library/math.html#math.gamma" title="math.gamma"><code class="xref py py-func docutils literal">gamma()</code></a> for the Gamma function, and

1326

<a class="reference internal" href="../library/math.html#math.lgamma" title="math.lgamma"><code class="xref py py-func docutils literal">lgamma()</code></a> for the natural log of the Gamma function.

1327

(Contributed by Mark Dickinson and nirinA raseliarison; <a class="reference external" href="https://bugs.python.org/issue3366">issue 3366</a>.)

1328

</li>

1329

<li>The <a class="reference internal" href="../library/multiprocessing.html#module-multiprocessing" title="multiprocessing: Process-based "threading" interface."><code class="xref py py-mod docutils literal">multiprocessing</code></a> module’s <code class="xref py py-class docutils literal">Manager*</code> classes

1330

can now be passed a callable that will be called whenever

1331

a subprocess is started, along with a set of arguments that will be

1332

passed to the callable.

1333

(Contributed by lekma; <a class="reference external" href="https://bugs.python.org/issue5585">issue 5585</a>.)

1334

The <code class="xref py py-class docutils literal">Pool</code> class, which controls a pool of worker processes,

1335

now has an optional maxtasksperchild parameter. Worker processes

1336

will perform the specified number of tasks and then exit, causing the

1337

<code class="xref py py-class docutils literal">Pool</code> to start a new worker. This is useful if tasks may leak

1338

memory or other resources, or if some tasks will cause the worker to

1339

become very large.

1340

(Contributed by Charles Cazabon; <a class="reference external" href="https://bugs.python.org/issue6963">issue 6963</a>.)

1341

</li>

1342

<li>The <a class="reference internal" href="../library/nntplib.html#module-nntplib" title="nntplib: NNTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal">nntplib</code></a> module now supports IPv6 addresses.

1343

(Contributed by Derek Morr; <a class="reference external" href="https://bugs.python.org/issue1664">issue 1664</a>.)

1344

</li>

1345

<li>New functions: the <a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal">os</code></a> module wraps the following POSIX system

1346

calls: <a class="reference internal" href="../library/os.html#os.getresgid" title="os.getresgid"><code class="xref py py-func docutils literal">getresgid()</code></a> and <a class="reference internal" href="../library/os.html#os.getresuid" title="os.getresuid"><code class="xref py py-func docutils literal">getresuid()</code></a>, which return the

1347

real, effective, and saved GIDs and UIDs;

1348

<a class="reference internal" href="../library/os.html#os.setresgid" title="os.setresgid"><code class="xref py py-func docutils literal">setresgid()</code></a> and <a class="reference internal" href="../library/os.html#os.setresuid" title="os.setresuid"><code class="xref py py-func docutils literal">setresuid()</code></a>, which set

1349

real, effective, and saved GIDs and UIDs to new values;

1350

<a class="reference internal" href="../library/os.html#os.initgroups" title="os.initgroups"><code class="xref py py-func docutils literal">initgroups()</code></a>, which initialize the group access list

1351

for the current process. (GID/UID functions

1352

contributed by Travis H.; <a class="reference external" href="https://bugs.python.org/issue6508">issue 6508</a>. Support for initgroups added

1353

by Jean-Paul Calderone; <a class="reference external" href="https://bugs.python.org/issue7333">issue 7333</a>.)

1354

The <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal">os.fork()</code></a> function now re-initializes the import lock in

1355

the child process; this fixes problems on Solaris when <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal">fork()</code></a>

1356

is called from a thread. (Fixed by Zsolt Cserna; <a class="reference external" href="https://bugs.python.org/issue7242">issue 7242</a>.)

1357

</li>

1358

<li>In the <a class="reference internal" href="../library/os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal">os.path</code></a> module, the <a class="reference internal" href="../library/os.path.html#os.path.normpath" title="os.path.normpath"><code class="xref py py-func docutils literal">normpath()</code></a> and

1359

<a class="reference internal" href="../library/os.path.html#os.path.abspath" title="os.path.abspath"><code class="xref py py-func docutils literal">abspath()</code></a> functions now preserve Unicode; if their input path

1360

is a Unicode string, the return value is also a Unicode string.

1361

(<a class="reference internal" href="../library/os.path.html#os.path.normpath" title="os.path.normpath"><code class="xref py py-meth docutils literal">normpath()</code></a> fixed by Matt Giuca in <a class="reference external" href="https://bugs.python.org/issue5827">issue 5827</a>;

1362

<a class="reference internal" href="../library/os.path.html#os.path.abspath" title="os.path.abspath"><code class="xref py py-meth docutils literal">abspath()</code></a> fixed by Ezio Melotti in <a class="reference external" href="https://bugs.python.org/issue3426">issue 3426</a>.)

1363

</li>

1364

<li>The <a class="reference internal" href="../library/pydoc.html#module-pydoc" title="pydoc: Documentation generator and online help system."><code class="xref py py-mod docutils literal">pydoc</code></a> module now has help for the various symbols that Python

1365

uses. You can now do <code class="docutils literal">help('<<')</code> or <code class="docutils literal">help('@')</code>, for example.

1366

(Contributed by David Laban; <a class="reference external" href="https://bugs.python.org/issue4739">issue 4739</a>.)

1367

</li>

1368

<li>The <a class="reference internal" href="../library/re.html#module-re" title="re: Regular expression operations."><code class="xref py py-mod docutils literal">re</code></a> module’s <a class="reference internal" href="../library/re.html#re.split" title="re.split"><code class="xref py py-func docutils literal">split()</code></a>, <a class="reference internal" href="../library/re.html#re.sub" title="re.sub"><code class="xref py py-func docutils literal">sub()</code></a>, and <a class="reference internal" href="../library/re.html#re.subn" title="re.subn"><code class="xref py py-func docutils literal">subn()</code></a>

1369

now accept an optional flags argument, for consistency with the

1370

other functions in the module. (Added by Gregory P. Smith.)

1371

</li>

1372

<li>New function: <a class="reference internal" href="../library/runpy.html#runpy.run_path" title="runpy.run_path"><code class="xref py py-func docutils literal">run_path()</code></a> in the <a class="reference internal" href="../library/runpy.html#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal">runpy</code></a> module

1373

will execute the code at a provided path argument. path can be

1374

the path of a Python source file (<code class="file docutils literal">example.py</code>), a compiled

1375

bytecode file (<code class="file docutils literal">example.pyc</code>), a directory

1376

(<code class="file docutils literal">./package/</code>), or a zip archive (<code class="file docutils literal">example.zip</code>). If a

1377

directory or zip path is provided, it will be added to the front of

1378

<code class="docutils literal">sys.path</code> and the module <a class="reference internal" href="../library/__main__.html#module-__main__" title="__main__: The environment where the top-level script is run."><code class="xref py py-mod docutils literal">__main__</code></a> will be imported. It’s

1379

expected that the directory or zip contains a <code class="file docutils literal">__main__.py</code>;

1380

if it doesn’t, some other <code class="file docutils literal">__main__.py</code> might be imported from

1381

a location later in <code class="docutils literal">sys.path</code>. This makes more of the machinery

1382

of <a class="reference internal" href="../library/runpy.html#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal">runpy</code></a> available to scripts that want to mimic the way

1383

Python’s command line processes an explicit path name.

1384

(Added by Nick Coghlan; <a class="reference external" href="https://bugs.python.org/issue6816">issue 6816</a>.)

1385

</li>

1386

<li>New function: in the <a class="reference internal" href="../library/shutil.html#module-shutil" title="shutil: High-level file operations, including copying."><code class="xref py py-mod docutils literal">shutil</code></a> module, <a class="reference internal" href="../library/shutil.html#shutil.make_archive" title="shutil.make_archive"><code class="xref py py-func docutils literal">make_archive()</code></a>

1387

takes a filename, archive type (zip or tar-format), and a directory

1388

path, and creates an archive containing the directory’s contents.

1389

(Added by Tarek Ziadé.)

1390

<a class="reference internal" href="../library/shutil.html#module-shutil" title="shutil: High-level file operations, including copying."><code class="xref py py-mod docutils literal">shutil</code></a>‘s <a class="reference internal" href="../library/shutil.html#shutil.copyfile" title="shutil.copyfile"><code class="xref py py-func docutils literal">copyfile()</code></a> and <a class="reference internal" href="../library/shutil.html#shutil.copytree" title="shutil.copytree"><code class="xref py py-func docutils literal">copytree()</code></a>

1391

functions now raise a <code class="xref py py-exc docutils literal">SpecialFileError</code> exception when

1392

asked to copy a named pipe. Previously the code would treat

1393

named pipes like a regular file by opening them for reading, and

1394

this would block indefinitely. (Fixed by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue3002">issue 3002</a>.)

1395

</li>

1396

<li>The <a class="reference internal" href="../library/signal.html#module-signal" title="signal: Set handlers for asynchronous events."><code class="xref py py-mod docutils literal">signal</code></a> module no longer re-installs the signal handler

1397

unless this is truly necessary, which fixes a bug that could make it

1398

impossible to catch the EINTR signal robustly. (Fixed by

1399

Charles-Francois Natali; <a class="reference external" href="https://bugs.python.org/issue8354">issue 8354</a>.)

1400

</li>

1401

<li>New functions: in the <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal">site</code></a> module, three new functions

1402

return various site- and user-specific paths.

1403

<a class="reference internal" href="../library/site.html#site.getsitepackages" title="site.getsitepackages"><code class="xref py py-func docutils literal">getsitepackages()</code></a> returns a list containing all

1404

global site-packages directories,

1405

<a class="reference internal" href="../library/site.html#site.getusersitepackages" title="site.getusersitepackages"><code class="xref py py-func docutils literal">getusersitepackages()</code></a> returns the path of the user’s

1406

site-packages directory, and

1407

<a class="reference internal" href="../library/site.html#site.getuserbase" title="site.getuserbase"><code class="xref py py-func docutils literal">getuserbase()</code></a> returns the value of the <code class="xref std std-envvar docutils literal">USER_BASE</code>

1408

environment variable, giving the path to a directory that can be used

1409

to store data.

1410

(Contributed by Tarek Ziadé; <a class="reference external" href="https://bugs.python.org/issue6693">issue 6693</a>.)

1411

The <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal">site</code></a> module now reports exceptions occurring

1412

when the <code class="xref py py-mod docutils literal">sitecustomize</code> module is imported, and will no longer

1413

catch and swallow the <a class="reference internal" href="../library/exceptions.html#exceptions.KeyboardInterrupt" title="exceptions.KeyboardInterrupt"><code class="xref py py-exc docutils literal">KeyboardInterrupt</code></a> exception. (Fixed by

1414

Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue3137">issue 3137</a>.)

1415

</li>

1416

<li>The <a class="reference internal" href="../library/socket.html#socket.create_connection" title="socket.create_connection"><code class="xref py py-func docutils literal">create_connection()</code></a> function

1417

gained a source_address parameter, a <code class="docutils literal">(host, port)</code> 2-tuple

1418

giving the source address that will be used for the connection.

1419

(Contributed by Eldon Ziegler; <a class="reference external" href="https://bugs.python.org/issue3972">issue 3972</a>.)

1420

The <a class="reference internal" href="../library/socket.html#socket.socket.recv_into" title="socket.socket.recv_into"><code class="xref py py-meth docutils literal">recv_into()</code></a> and <a class="reference internal" href="../library/socket.html#socket.socket.recvfrom_into" title="socket.socket.recvfrom_into"><code class="xref py py-meth docutils literal">recvfrom_into()</code></a>

1421

methods will now write into objects that support the buffer API, most usefully

1422

the <a class="reference internal" href="../library/functions.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal">bytearray</code></a> and <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal">memoryview</code></a> objects. (Implemented by

1423

Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue8104">issue 8104</a>.)

1424

</li>

1425

<li>The <a class="reference internal" href="../library/socketserver.html#module-SocketServer" title="SocketServer: A framework for network servers."><code class="xref py py-mod docutils literal">SocketServer</code></a> module’s <code class="xref py py-class docutils literal">TCPServer</code> class now

1426

supports socket timeouts and disabling the Nagle algorithm.

1427

The <code class="xref py py-attr docutils literal">disable_nagle_algorithm</code> class attribute

1428

defaults to False; if overridden to be True,

1429

new request connections will have the TCP_NODELAY option set to

1430

prevent buffering many small sends into a single TCP packet.

1431

The <a class="reference internal" href="../library/socketserver.html#SocketServer.BaseServer.timeout" title="SocketServer.BaseServer.timeout"><code class="xref py py-attr docutils literal">timeout</code></a> class attribute can hold

1432

a timeout in seconds that will be applied to the request socket; if

1433

no request is received within that time, <a class="reference internal" href="../library/socketserver.html#SocketServer.BaseServer.handle_timeout" title="SocketServer.BaseServer.handle_timeout"><code class="xref py py-meth docutils literal">handle_timeout()</code></a>

1434

will be called and <a class="reference internal" href="../library/socketserver.html#SocketServer.BaseServer.handle_request" title="SocketServer.BaseServer.handle_request"><code class="xref py py-meth docutils literal">handle_request()</code></a> will return.

1435

(Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue6192">issue 6192</a> and <a class="reference external" href="https://bugs.python.org/issue6267">issue 6267</a>.)

1436

</li>

1437

<li>Updated module: the <a class="reference internal" href="../library/sqlite3.html#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal">sqlite3</code></a> module has been updated to

1438

version 2.6.0 of the <a class="reference external" href="http://code.google.com/p/pysqlite/">pysqlite package</a>. Version 2.6.0 includes a number of bugfixes, and adds

1439

the ability to load SQLite extensions from shared libraries.

1440

Call the <code class="docutils literal">enable_load_extension(True)</code> method to enable extensions,

1441

and then call <a class="reference internal" href="../library/sqlite3.html#sqlite3.Connection.load_extension" title="sqlite3.Connection.load_extension"><code class="xref py py-meth docutils literal">load_extension()</code></a> to load a particular shared library.

1442

(Updated by Gerhard Häring.)

1443

</li>

1444

<li>The <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal">ssl</code></a> module’s <code class="xref py py-class docutils literal">SSLSocket</code> objects now support the

1445

buffer API, which fixed a test suite failure (fix by Antoine Pitrou;

1446

<a class="reference external" href="https://bugs.python.org/issue7133">issue 7133</a>) and automatically set

1447

OpenSSL’s <code class="xref c c-macro docutils literal">SSL_MODE_AUTO_RETRY</code>, which will prevent an error

1448

code being returned from <code class="xref py py-meth docutils literal">recv()</code> operations that trigger an SSL

1449

renegotiation (fix by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue8222">issue 8222</a>).

1450

The <a class="reference internal" href="../library/ssl.html#ssl.wrap_socket" title="ssl.wrap_socket"><code class="xref py py-func docutils literal">ssl.wrap_socket()</code></a> constructor function now takes a

1451

ciphers argument that’s a string listing the encryption algorithms

1452

to be allowed; the format of the string is described

1453

<a class="reference external" href="http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT">in the OpenSSL documentation</a>.

1454

(Added by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue8322">issue 8322</a>.)

1455

Another change makes the extension load all of OpenSSL’s ciphers and

1456

digest algorithms so that they’re all available. Some SSL

1457

certificates couldn’t be verified, reporting an “unknown algorithm”

1458

error. (Reported by Beda Kosata, and fixed by Antoine Pitrou;

1459

<a class="reference external" href="https://bugs.python.org/issue8484">issue 8484</a>.)

1460

The version of OpenSSL being used is now available as the module

1461

attributes <a class="reference internal" href="../library/ssl.html#ssl.OPENSSL_VERSION" title="ssl.OPENSSL_VERSION"><code class="xref py py-data docutils literal">ssl.OPENSSL_VERSION</code></a> (a string),

1462

<a class="reference internal" href="../library/ssl.html#ssl.OPENSSL_VERSION_INFO" title="ssl.OPENSSL_VERSION_INFO"><code class="xref py py-data docutils literal">ssl.OPENSSL_VERSION_INFO</code></a> (a 5-tuple), and

1463

<a class="reference internal" href="../library/ssl.html#ssl.OPENSSL_VERSION_NUMBER" title="ssl.OPENSSL_VERSION_NUMBER"><code class="xref py py-data docutils literal">ssl.OPENSSL_VERSION_NUMBER</code></a> (an integer). (Added by Antoine

1464

Pitrou; <a class="reference external" href="https://bugs.python.org/issue8321">issue 8321</a>.)

1465

</li>

1466

<li>The <a class="reference internal" href="../library/struct.html#module-struct" title="struct: Interpret strings as packed binary data."><code class="xref py py-mod docutils literal">struct</code></a> module will no longer silently ignore overflow

1467

errors when a value is too large for a particular integer format

1468

code (one of <code class="docutils literal">bBhHiIlLqQ</code>); it now always raises a

1469

<a class="reference internal" href="../library/struct.html#struct.error" title="struct.error"><code class="xref py py-exc docutils literal">struct.error</code></a> exception. (Changed by Mark Dickinson;

1470

<a class="reference external" href="https://bugs.python.org/issue1523">issue 1523</a>.) The <a class="reference internal" href="../library/struct.html#struct.pack" title="struct.pack"><code class="xref py py-func docutils literal">pack()</code></a> function will also

1471

attempt to use <a class="reference internal" href="../reference/datamodel.html#object.__index__" title="object.__index__"><code class="xref py py-meth docutils literal">__index__()</code></a> to convert and pack non-integers

1472

before trying the <a class="reference internal" href="../reference/datamodel.html#object.__int__" title="object.__int__"><code class="xref py py-meth docutils literal">__int__()</code></a> method or reporting an error.

1473

(Changed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue8300">issue 8300</a>.)

1474

</li>

1475

<li>New function: the <a class="reference internal" href="../library/subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a> module’s

1476

<a class="reference internal" href="../library/subprocess.html#subprocess.check_output" title="subprocess.check_output"><code class="xref py py-func docutils literal">check_output()</code></a> runs a command with a specified set of arguments

1477

and returns the command’s output as a string when the command runs without

1478

error, or raises a <a class="reference internal" href="../library/subprocess.html#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal">CalledProcessError</code></a> exception otherwise.

1479

<div class="highlight-python"><div class="highlight"><pre>>>> subprocess.check_output(['df', '-h', '.'])

1480

'Filesystem Size Used Avail Capacity Mounted on\n

1481

/dev/disk0s2 52G 49G 3.0G 94% /\n'

1482

1483

>>> subprocess.check_output(['df', '-h', '/bogus'])

1484

...

1485

subprocess.CalledProcessError: Command '['df', '-h', '/bogus']' returned non-zero exit status 1

1486

</pre></div>

1487

</div>

1488

(Contributed by Gregory P. Smith.)

1489

The <a class="reference internal" href="../library/subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal">subprocess</code></a> module will now retry its internal system calls

1490

on receiving an <code class="xref py py-const docutils literal">EINTR</code> signal. (Reported by several people; final

1491

patch by Gregory P. Smith in <a class="reference external" href="https://bugs.python.org/issue1068268">issue 1068268</a>.)

1492

</li>

1493

<li>New function: <a class="reference internal" href="../library/symtable.html#symtable.Symbol.is_declared_global" title="symtable.Symbol.is_declared_global"><code class="xref py py-func docutils literal">is_declared_global()</code></a> in the <a class="reference internal" href="../library/symtable.html#module-symtable" title="symtable: Interface to the compiler's internal symbol tables."><code class="xref py py-mod docutils literal">symtable</code></a> module

1494

returns true for variables that are explicitly declared to be global,

1495

false for ones that are implicitly global.

1496

(Contributed by Jeremy Hylton.)

1497

</li>

1498

<li>The <a class="reference internal" href="../library/syslog.html#module-syslog" title="syslog: An interface to the Unix syslog library routines. (Unix)"><code class="xref py py-mod docutils literal">syslog</code></a> module will now use the value of <code class="docutils literal">sys.argv[0]</code> as the

1499

identifier instead of the previous default value of <code class="docutils literal">'python'</code>.

1500

(Changed by Sean Reifschneider; <a class="reference external" href="https://bugs.python.org/issue8451">issue 8451</a>.)

1501

</li>

1502

<li>The <code class="docutils literal">sys.version_info</code> value is now a named tuple, with attributes

1503

named <code class="xref py py-attr docutils literal">major</code>, <code class="xref py py-attr docutils literal">minor</code>, <code class="xref py py-attr docutils literal">micro</code>,

1504

<code class="xref py py-attr docutils literal">releaselevel</code>, and <code class="xref py py-attr docutils literal">serial</code>. (Contributed by Ross

1505

Light; <a class="reference external" href="https://bugs.python.org/issue4285">issue 4285</a>.)

1506

<a class="reference internal" href="../library/sys.html#sys.getwindowsversion" title="sys.getwindowsversion"><code class="xref py py-func docutils literal">sys.getwindowsversion()</code></a> also returns a named tuple,

1507

with attributes named <code class="xref py py-attr docutils literal">major</code>, <code class="xref py py-attr docutils literal">minor</code>, <code class="xref py py-attr docutils literal">build</code>,

1508

<a class="reference internal" href="../library/platform.html#module-platform" title="platform: Retrieves as much platform identifying data as possible."><code class="xref py py-attr docutils literal">platform</code></a>, <code class="xref py py-attr docutils literal">service_pack</code>, <code class="xref py py-attr docutils literal">service_pack_major</code>,

1509

<code class="xref py py-attr docutils literal">service_pack_minor</code>, <code class="xref py py-attr docutils literal">suite_mask</code>, and

1510

<code class="xref py py-attr docutils literal">product_type</code>. (Contributed by Brian Curtin; <a class="reference external" href="https://bugs.python.org/issue7766">issue 7766</a>.)

1511

</li>

1512

<li>The <a class="reference internal" href="../library/tarfile.html#module-tarfile" title="tarfile: Read and write tar-format archive files."><code class="xref py py-mod docutils literal">tarfile</code></a> module’s default error handling has changed, to

1513

no longer suppress fatal errors. The default error level was previously 0,

1514

which meant that errors would only result in a message being written to the

1515

debug log, but because the debug log is not activated by default,

1516

these errors go unnoticed. The default error level is now 1,

1517

which raises an exception if there’s an error.

1518

(Changed by Lars Gustäbel; <a class="reference external" href="https://bugs.python.org/issue7357">issue 7357</a>.)

1519

<a class="reference internal" href="../library/tarfile.html#module-tarfile" title="tarfile: Read and write tar-format archive files."><code class="xref py py-mod docutils literal">tarfile</code></a> now supports filtering the <a class="reference internal" href="../library/tarfile.html#tarfile.TarInfo" title="tarfile.TarInfo"><code class="xref py py-class docutils literal">TarInfo</code></a>

1520

objects being added to a tar file. When you call <a class="reference internal" href="../library/tarfile.html#tarfile.TarFile.add" title="tarfile.TarFile.add"><code class="xref py py-meth docutils literal">add()</code></a>,

1521

you may supply an optional filter argument

1522

that’s a callable. The filter callable will be passed the

1523

<a class="reference internal" href="../library/tarfile.html#tarfile.TarInfo" title="tarfile.TarInfo"><code class="xref py py-class docutils literal">TarInfo</code></a> for every file being added, and can modify and return it.

1524

If the callable returns <code class="docutils literal">None</code>, the file will be excluded from the

1525

resulting archive. This is more powerful than the existing

1526

exclude argument, which has therefore been deprecated.

1527

(Added by Lars Gustäbel; <a class="reference external" href="https://bugs.python.org/issue6856">issue 6856</a>.)

1528

The <a class="reference internal" href="../library/tarfile.html#tarfile.TarFile" title="tarfile.TarFile"><code class="xref py py-class docutils literal">TarFile</code></a> class also now supports the context management protocol.

1529

(Added by Lars Gustäbel; <a class="reference external" href="https://bugs.python.org/issue7232">issue 7232</a>.)

1530

</li>

1531

<li>The <a class="reference internal" href="../library/threading.html#threading.Event.wait" title="threading.Event.wait"><code class="xref py py-meth docutils literal">wait()</code></a> method of the <a class="reference internal" href="../library/threading.html#threading.Event" title="threading.Event"><code class="xref py py-class docutils literal">threading.Event</code></a> class

1532

now returns the internal flag on exit. This means the method will usually

1533

return true because <a class="reference internal" href="../library/threading.html#threading.Event.wait" title="threading.Event.wait"><code class="xref py py-meth docutils literal">wait()</code></a> is supposed to block until the

1534

internal flag becomes true. The return value will only be false if

1535

a timeout was provided and the operation timed out.

1536

(Contributed by Tim Lesher; <a class="reference external" href="https://bugs.python.org/issue1674032">issue 1674032</a>.)

1537

</li>

1538

<li>The Unicode database provided by the <a class="reference internal" href="../library/unicodedata.html#module-unicodedata" title="unicodedata: Access the Unicode Database."><code class="xref py py-mod docutils literal">unicodedata</code></a> module is

1539

now used internally to determine which characters are numeric,

1540

whitespace, or represent line breaks. The database also

1541

includes information from the <code class="file docutils literal">Unihan.txt</code> data file (patch

1542

by Anders Chrigström and Amaury Forgeot d’Arc; <a class="reference external" href="https://bugs.python.org/issue1571184">issue 1571184</a>)

1543

and has been updated to version 5.2.0 (updated by

1544

Florent Xicluna; <a class="reference external" href="https://bugs.python.org/issue8024">issue 8024</a>).

1545

</li>

1546

<li>The <a class="reference internal" href="../library/urlparse.html#module-urlparse" title="urlparse: Parse URLs into or assemble them from components."><code class="xref py py-mod docutils literal">urlparse</code></a> module’s <a class="reference internal" href="../library/urlparse.html#urlparse.urlsplit" title="urlparse.urlsplit"><code class="xref py py-func docutils literal">urlsplit()</code></a> now handles

1547

unknown URL schemes in a fashion compliant with <a class="rfc reference external" href="https://tools.ietf.org/html/rfc3986.html">RFC 3986</a>: if the

1548

URL is of the form <code class="docutils literal">"<something>://..."</code>, the text before the

1549

<code class="docutils literal">://</code> is treated as the scheme, even if it’s a made-up scheme that

1550

the module doesn’t know about. This change may break code that

1551

worked around the old behaviour. For example, Python 2.6.4 or 2.5

1552

will return the following:

1553

<div class="highlight-python"><div class="highlight"><pre>>>> import urlparse

1554

>>> urlparse.urlsplit('invented://host/filename?query')

1555

('invented', '', '//host/filename?query', '', '')

1556

</pre></div>

1557

</div>

1558

Python 2.7 (and Python 2.6.5) will return:

1559

<div class="highlight-python"><div class="highlight"><pre>>>> import urlparse

1560

1561

('invented', 'host', '/filename?query', '', '')

1562

</pre></div>

1563

</div>

1564

(Python 2.7 actually produces slightly different output, since it

1565

returns a named tuple instead of a standard tuple.)

1566

The <a class="reference internal" href="../library/urlparse.html#module-urlparse" title="urlparse: Parse URLs into or assemble them from components."><code class="xref py py-mod docutils literal">urlparse</code></a> module also supports IPv6 literal addresses as defined by

1567

<a class="rfc reference external" href="https://tools.ietf.org/html/rfc2732.html">RFC 2732</a> (contributed by Senthil Kumaran; <a class="reference external" href="https://bugs.python.org/issue2987">issue 2987</a>).

1568

<div class="highlight-python"><div class="highlight"><pre>>>> urlparse.urlparse('http://[1080::8:800:200C:417A]/foo')

1569

ParseResult(scheme='http', netloc='[1080::8:800:200C:417A]',

1570

path='/foo', params='', query='', fragment='')

1571

</pre></div>

1572

</div>

1573

</li>

1574

<li>New class: the <a class="reference internal" href="../library/weakref.html#weakref.WeakSet" title="weakref.WeakSet"><code class="xref py py-class docutils literal">WeakSet</code></a> class in the <a class="reference internal" href="../library/weakref.html#module-weakref" title="weakref: Support for weak references and weak dictionaries."><code class="xref py py-mod docutils literal">weakref</code></a>

1575

module is a set that only holds weak references to its elements; elements

1576

will be removed once there are no references pointing to them.

1577

(Originally implemented in Python 3.x by Raymond Hettinger, and backported

1578

to 2.7 by Michael Foord.)

1579

</li>

1580

<li>The ElementTree library, <code class="xref py py-mod docutils literal">xml.etree</code>, no longer escapes

1581

ampersands and angle brackets when outputting an XML processing

1582

instruction (which looks like <code class="docutils literal"><?xml-stylesheet href="#style1"?></code>)

1583

or comment (which looks like <code class="docutils literal"></code>).

1584

(Patch by Neil Muller; <a class="reference external" href="https://bugs.python.org/issue2746">issue 2746</a>.)

1585

</li>

1586

<li>The XML-RPC client and server, provided by the <a class="reference internal" href="../library/xmlrpclib.html#module-xmlrpclib" title="xmlrpclib: XML-RPC client access."><code class="xref py py-mod docutils literal">xmlrpclib</code></a> and

1587

<a class="reference internal" href="../library/simplexmlrpcserver.html#module-SimpleXMLRPCServer" title="SimpleXMLRPCServer: Basic XML-RPC server implementation."><code class="xref py py-mod docutils literal">SimpleXMLRPCServer</code></a> modules, have improved performance by

1588

supporting HTTP/1.1 keep-alive and by optionally using gzip encoding

1589

to compress the XML being exchanged. The gzip compression is

1590

controlled by the <code class="xref py py-attr docutils literal">encode_threshold</code> attribute of

1591

<code class="xref py py-class docutils literal">SimpleXMLRPCRequestHandler</code>, which contains a size in bytes;

1592

responses larger than this will be compressed.

1593

(Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue6267">issue 6267</a>.)

1594

</li>

1595

<li>The <a class="reference internal" href="../library/zipfile.html#module-zipfile" title="zipfile: Read and write ZIP-format archive files."><code class="xref py py-mod docutils literal">zipfile</code></a> module’s <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile" title="zipfile.ZipFile"><code class="xref py py-class docutils literal">ZipFile</code></a> now supports the context

1596

management protocol, so you can write <code class="docutils literal">with zipfile.ZipFile(...) as f:</code>.

1597

(Contributed by Brian Curtin; <a class="reference external" href="https://bugs.python.org/issue5511">issue 5511</a>.)

1598

<a class="reference internal" href="../library/zipfile.html#module-zipfile" title="zipfile: Read and write ZIP-format archive files."><code class="xref py py-mod docutils literal">zipfile</code></a> now also supports archiving empty directories and

1599

extracts them correctly. (Fixed by Kuba Wieczorek; <a class="reference external" href="https://bugs.python.org/issue4710">issue 4710</a>.)

1600

Reading files out of an archive is faster, and interleaving

1601

<a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile.read" title="zipfile.ZipFile.read"><code class="xref py py-meth docutils literal">read()</code></a> and <code class="xref py py-meth docutils literal">readline()</code> now works correctly.

1602

(Contributed by Nir Aides; <a class="reference external" href="https://bugs.python.org/issue7610">issue 7610</a>.)

1603

The <a class="reference internal" href="../library/zipfile.html#zipfile.is_zipfile" title="zipfile.is_zipfile"><code class="xref py py-func docutils literal">is_zipfile()</code></a> function now

1604

accepts a file object, in addition to the path names accepted in earlier

1605

versions. (Contributed by Gabriel Genellina; <a class="reference external" href="https://bugs.python.org/issue4756">issue 4756</a>.)

1606

The <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile.writestr" title="zipfile.ZipFile.writestr"><code class="xref py py-meth docutils literal">writestr()</code></a> method now has an optional compress_type parameter

1607

that lets you override the default compression method specified in the

1608

<a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile" title="zipfile.ZipFile"><code class="xref py py-class docutils literal">ZipFile</code></a> constructor. (Contributed by Ronald Oussoren;

1609

<a class="reference external" href="https://bugs.python.org/issue6003">issue 6003</a>.)

1610

</li>

1611

</ul>

1612

1613

<h3>New module: importlib<a class="headerlink" href="#new-module-importlib" title="Permalink to this headline">¶</a></h3>

1614

Python 3.1 includes the <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: Convenience wrappers for __import__"><code class="xref py py-mod docutils literal">importlib</code></a> package, a re-implementation

1615

of the logic underlying Python’s <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal">import</code></a> statement.

1616

<a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: Convenience wrappers for __import__"><code class="xref py py-mod docutils literal">importlib</code></a> is useful for implementors of Python interpreters and

1617

to users who wish to write new importers that can participate in the

1618

import process. Python 2.7 doesn’t contain the complete

1619

<a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: Convenience wrappers for __import__"><code class="xref py py-mod docutils literal">importlib</code></a> package, but instead has a tiny subset that contains

1620

a single function, <a class="reference internal" href="../library/importlib.html#importlib.import_module" title="importlib.import_module"><code class="xref py py-func docutils literal">import_module()</code></a>.

1621

<code class="docutils literal">import_module(name, package=None)</code> imports a module. name is

1622

a string containing the module or package’s name. It’s possible to do

1623

relative imports by providing a string that begins with a <code class="docutils literal">.</code>

1624

character, such as <code class="docutils literal">..utils.errors</code>. For relative imports, the

1625

package argument must be provided and is the name of the package that

1626

will be used as the anchor for

1627

the relative import. <a class="reference internal" href="../library/importlib.html#importlib.import_module" title="importlib.import_module"><code class="xref py py-func docutils literal">import_module()</code></a> both inserts the imported

1628

module into <code class="docutils literal">sys.modules</code> and returns the module object.

1629

Here are some examples:

1630

<div class="highlight-python"><div class="highlight"><pre>>>> from importlib import import_module

1631

>>> anydbm = import_module('anydbm') # Standard absolute import

1632

>>> anydbm

1633

1634

>>> # Relative import

1635

>>> file_util = import_module('..file_util', 'distutils.command')

1636

>>> file_util

1637

1638

</pre></div>

1639

</div>

1640

<a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: Convenience wrappers for __import__"><code class="xref py py-mod docutils literal">importlib</code></a> was implemented by Brett Cannon and introduced in

1641

Python 3.1.

1642

</div>

1643

1644

<h3>New module: sysconfig<a class="headerlink" href="#new-module-sysconfig" title="Permalink to this headline">¶</a></h3>

1645

The <a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal">sysconfig</code></a> module has been pulled out of the Distutils

1646

package, becoming a new top-level module in its own right.

1647

<a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal">sysconfig</code></a> provides functions for getting information about

1648

Python’s build process: compiler switches, installation paths, the

1649

platform name, and whether Python is running from its source

1650

directory.

1651

Some of the functions in the module are:

1652

1653

<li><a class="reference internal" href="../library/sysconfig.html#sysconfig.get_config_var" title="sysconfig.get_config_var"><code class="xref py py-func docutils literal">get_config_var()</code></a> returns variables from Python’s

1654

Makefile and the <code class="file docutils literal">pyconfig.h</code> file.</li>

1655

<li><a class="reference internal" href="../library/sysconfig.html#sysconfig.get_config_vars" title="sysconfig.get_config_vars"><code class="xref py py-func docutils literal">get_config_vars()</code></a> returns a dictionary containing

1656

all of the configuration variables.</li>

1657

<li><a class="reference internal" href="../library/sysconfig.html#sysconfig.get_path" title="sysconfig.get_path"><code class="xref py py-func docutils literal">get_path()</code></a> returns the configured path for

1658

a particular type of module: the standard library,

1659

site-specific modules, platform-specific modules, etc.</li>

1660

<li><a class="reference internal" href="../library/sysconfig.html#sysconfig.is_python_build" title="sysconfig.is_python_build"><code class="xref py py-func docutils literal">is_python_build()</code></a> returns true if you’re running a

1661

binary from a Python source tree, and false otherwise.</li>

1662

</ul>

1663

Consult the <a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal">sysconfig</code></a> documentation for more details and for

1664

a complete list of functions.

1665

The Distutils package and <a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal">sysconfig</code></a> are now maintained by Tarek

1666

Ziadé, who has also started a Distutils2 package (source repository at

1667

<a class="reference external" href="https://hg.python.org/distutils2/">https://hg.python.org/distutils2/</a>) for developing a next-generation

1668

version of Distutils.

1669

</div>

1670

1671

<h3>ttk: Themed Widgets for Tk<a class="headerlink" href="#ttk-themed-widgets-for-tk" title="Permalink to this headline">¶</a></h3>

1672

Tcl/Tk 8.5 includes a set of themed widgets that re-implement basic Tk

1673

widgets but have a more customizable appearance and can therefore more

1674

closely resemble the native platform’s widgets. This widget

1675

set was originally called Tile, but was renamed to Ttk (for “themed Tk”)

1676

on being added to Tcl/Tck release 8.5.

1677

To learn more, read the <a class="reference internal" href="../library/ttk.html#module-ttk" title="ttk: Tk themed widget set"><code class="xref py py-mod docutils literal">ttk</code></a> module documentation. You may also

1678

wish to read the Tcl/Tk manual page describing the

1679

Ttk theme engine, available at

1680

<a class="reference external" href="http://www.tcl.tk/man/tcl8.5/TkCmd/ttk_intro.htm">http://www.tcl.tk/man/tcl8.5/TkCmd/ttk_intro.htm</a>. Some

1681

screenshots of the Python/Ttk code in use are at

1682

<a class="reference external" href="http://code.google.com/p/python-ttk/wiki/Screenshots">http://code.google.com/p/python-ttk/wiki/Screenshots</a>.

1683

The <a class="reference internal" href="../library/ttk.html#module-ttk" title="ttk: Tk themed widget set"><code class="xref py py-mod docutils literal">ttk</code></a> module was written by Guilherme Polo and added in

1684

<a class="reference external" href="https://bugs.python.org/issue2983">issue 2983</a>. An alternate version called <code class="docutils literal">Tile.py</code>, written by

1685

Martin Franklin and maintained by Kevin Walzer, was proposed for

1686

inclusion in <a class="reference external" href="https://bugs.python.org/issue2618">issue 2618</a>, but the authors argued that Guilherme

1687

Polo’s work was more comprehensive.

1688

</div>

1689

1690

<h3>Updated module: unittest<a class="headerlink" href="#updated-module-unittest" title="Permalink to this headline">¶</a></h3>

1691

The <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal">unittest</code></a> module was greatly enhanced; many

1692

new features were added. Most of these features were implemented

1693

by Michael Foord, unless otherwise noted. The enhanced version of

1694

the module is downloadable separately for use with Python versions 2.4 to 2.6,

1695

packaged as the <code class="xref py py-mod docutils literal">unittest2</code> package, from

1696

<a class="reference external" href="https://pypi.python.org/pypi/unittest2">https://pypi.python.org/pypi/unittest2</a>.

1697

When used from the command line, the module can automatically discover

1698

tests. It’s not as fancy as <a class="reference external" href="http://pytest.org">py.test</a> or

1699

<a class="reference external" href="http://code.google.com/p/python-nose/">nose</a>, but provides a simple way

1700

to run tests kept within a set of package directories. For example,

1701

the following command will search the <code class="file docutils literal">test/</code> subdirectory for

1702

any importable test files named <code class="docutils literal">test*.py</code>:

1703

<div class="highlight-python"><div class="highlight"><pre>python -m unittest discover -s test

1704

</pre></div>

1705

</div>

1706

Consult the <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal">unittest</code></a> module documentation for more details.

1707

(Developed in <a class="reference external" href="https://bugs.python.org/issue6001">issue 6001</a>.)

1708

The <a class="reference internal" href="../library/unittest.html#unittest.main" title="unittest.main"><code class="xref py py-func docutils literal">main()</code></a> function supports some other new options:

1709

<ul>

1710

<li><code class="xref std std-option docutils literal">-b</code> or <code class="xref std std-option docutils literal">--buffer</code> will buffer the standard output

1711

and standard error streams during each test. If the test passes,

1712

any resulting output will be discarded; on failure, the buffered

1713

output will be displayed.

1714

</li>

1715

<li><a class="reference internal" href="../using/cmdline.html#cmdoption-c"><code class="xref std std-option docutils literal">-c</code></a> or <code class="xref std std-option docutils literal">--catch</code> will cause the control-C interrupt

1716

to be handled more gracefully. Instead of interrupting the test

1717

process immediately, the currently running test will be completed

1718

and then the partial results up to the interruption will be reported.

1719

If you’re impatient, a second press of control-C will cause an immediate

1720

interruption.

1721

This control-C handler tries to avoid causing problems when the code

1722

being tested or the tests being run have defined a signal handler of

1723

their own, by noticing that a signal handler was already set and

1724

calling it. If this doesn’t work for you, there’s a

1725

<a class="reference internal" href="../library/unittest.html#unittest.removeHandler" title="unittest.removeHandler"><code class="xref py py-func docutils literal">removeHandler()</code></a> decorator that can be used to mark tests that

1726

should have the control-C handling disabled.

1727

</li>

1728

<li><code class="xref std std-option docutils literal">-f</code> or <code class="xref std std-option docutils literal">--failfast</code> makes

1729

test execution stop immediately when a test fails instead of

1730

continuing to execute further tests. (Suggested by Cliff Dyer and

1731

implemented by Michael Foord; <a class="reference external" href="https://bugs.python.org/issue8074">issue 8074</a>.)

1732

</li>

1733

</ul>

1734

The progress messages now show ‘x’ for expected failures

1735

and ‘u’ for unexpected successes when run in verbose mode.

1736

(Contributed by Benjamin Peterson.)

1737

Test cases can raise the <a class="reference internal" href="../library/unittest.html#unittest.SkipTest" title="unittest.SkipTest"><code class="xref py py-exc docutils literal">SkipTest</code></a> exception to skip a

1738

test (<a class="reference external" href="https://bugs.python.org/issue1034053">issue 1034053</a>).

1739

The error messages for <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal">assertEqual()</code></a>,

1740

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertTrue" title="unittest.TestCase.assertTrue"><code class="xref py py-meth docutils literal">assertTrue()</code></a>, and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertFalse" title="unittest.TestCase.assertFalse"><code class="xref py py-meth docutils literal">assertFalse()</code></a>

1741

failures now provide more information. If you set the

1742

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.longMessage" title="unittest.TestCase.longMessage"><code class="xref py py-attr docutils literal">longMessage</code></a> attribute of your <a class="reference internal" href="../library/unittest.html#unittest.TestCase" title="unittest.TestCase"><code class="xref py py-class docutils literal">TestCase</code></a> classes to

1743

True, both the standard error message and any additional message you

1744

provide will be printed for failures. (Added by Michael Foord; <a class="reference external" href="https://bugs.python.org/issue5663">issue 5663</a>.)

1745

The <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertRaises" title="unittest.TestCase.assertRaises"><code class="xref py py-meth docutils literal">assertRaises()</code></a> method now

1746

returns a context handler when called without providing a callable

1747

object to run. For example, you can write this:

1748

<div class="highlight-python"><div class="highlight"><pre>with self.assertRaises(KeyError):

1749

{}['foo']

1750

</pre></div>

1751

</div>

1752

(Implemented by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue4444">issue 4444</a>.)

1753

Module- and class-level setup and teardown fixtures are now supported.

1754

Modules can contain <code class="xref py py-func docutils literal">setUpModule()</code> and <code class="xref py py-func docutils literal">tearDownModule()</code>

1755

functions. Classes can have <a class="reference internal" href="../library/unittest.html#unittest.TestCase.setUpClass" title="unittest.TestCase.setUpClass"><code class="xref py py-meth docutils literal">setUpClass()</code></a> and

1756

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.tearDownClass" title="unittest.TestCase.tearDownClass"><code class="xref py py-meth docutils literal">tearDownClass()</code></a> methods that must be defined as class methods

1757

(using <code class="docutils literal">@classmethod</code> or equivalent). These functions and

1758

methods are invoked when the test runner switches to a test case in a

1759

different module or class.

1760

The methods <a class="reference internal" href="../library/unittest.html#unittest.TestCase.addCleanup" title="unittest.TestCase.addCleanup"><code class="xref py py-meth docutils literal">addCleanup()</code></a> and

1761

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.doCleanups" title="unittest.TestCase.doCleanups"><code class="xref py py-meth docutils literal">doCleanups()</code></a> were added.

1762

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.addCleanup" title="unittest.TestCase.addCleanup"><code class="xref py py-meth docutils literal">addCleanup()</code></a> lets you add cleanup functions that

1763

will be called unconditionally (after <a class="reference internal" href="../library/unittest.html#unittest.TestCase.setUp" title="unittest.TestCase.setUp"><code class="xref py py-meth docutils literal">setUp()</code></a> if

1764

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.setUp" title="unittest.TestCase.setUp"><code class="xref py py-meth docutils literal">setUp()</code></a> fails, otherwise after <a class="reference internal" href="../library/unittest.html#unittest.TestCase.tearDown" title="unittest.TestCase.tearDown"><code class="xref py py-meth docutils literal">tearDown()</code></a>). This allows

1765

for much simpler resource allocation and deallocation during tests

1766

(<a class="reference external" href="https://bugs.python.org/issue5679">issue 5679</a>).

1767

A number of new methods were added that provide more specialized

1768

tests. Many of these methods were written by Google engineers

1769

for use in their test suites; Gregory P. Smith, Michael Foord, and

1770

GvR worked on merging them into Python’s version of <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal">unittest</code></a>.

1771

1772

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsNone" title="unittest.TestCase.assertIsNone"><code class="xref py py-meth docutils literal">assertIsNone()</code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsNotNone" title="unittest.TestCase.assertIsNotNone"><code class="xref py py-meth docutils literal">assertIsNotNone()</code></a> take one

1773

expression and verify that the result is or is not <code class="docutils literal">None</code>.</li>

1774

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIs" title="unittest.TestCase.assertIs"><code class="xref py py-meth docutils literal">assertIs()</code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsNot" title="unittest.TestCase.assertIsNot"><code class="xref py py-meth docutils literal">assertIsNot()</code></a>

1775

take two values and check whether the two values evaluate to the same object or not.

1776

(Added by Michael Foord; <a class="reference external" href="https://bugs.python.org/issue2578">issue 2578</a>.)</li>

1777

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsInstance" title="unittest.TestCase.assertIsInstance"><code class="xref py py-meth docutils literal">assertIsInstance()</code></a> and

1778

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNotIsInstance" title="unittest.TestCase.assertNotIsInstance"><code class="xref py py-meth docutils literal">assertNotIsInstance()</code></a> check whether

1779

the resulting object is an instance of a particular class, or of

1780

one of a tuple of classes. (Added by Georg Brandl; <a class="reference external" href="https://bugs.python.org/issue7031">issue 7031</a>.)</li>

1781

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertGreater" title="unittest.TestCase.assertGreater"><code class="xref py py-meth docutils literal">assertGreater()</code></a>, <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertGreaterEqual" title="unittest.TestCase.assertGreaterEqual"><code class="xref py py-meth docutils literal">assertGreaterEqual()</code></a>,

1782

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertLess" title="unittest.TestCase.assertLess"><code class="xref py py-meth docutils literal">assertLess()</code></a>, and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertLessEqual" title="unittest.TestCase.assertLessEqual"><code class="xref py py-meth docutils literal">assertLessEqual()</code></a> compare

1783

two quantities.</li>

1784

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertMultiLineEqual" title="unittest.TestCase.assertMultiLineEqual"><code class="xref py py-meth docutils literal">assertMultiLineEqual()</code></a> compares two strings, and if they’re

1785

not equal, displays a helpful comparison that highlights the

1786

differences in the two strings. This comparison is now used by

1787

default when Unicode strings are compared with <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal">assertEqual()</code></a>.</li>

1788

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertRegexpMatches" title="unittest.TestCase.assertRegexpMatches"><code class="xref py py-meth docutils literal">assertRegexpMatches()</code></a> and

1789

<a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNotRegexpMatches" title="unittest.TestCase.assertNotRegexpMatches"><code class="xref py py-meth docutils literal">assertNotRegexpMatches()</code></a> checks whether the

1790

first argument is a string matching or not matching the regular

1791

expression provided as the second argument (<a class="reference external" href="https://bugs.python.org/issue8038">issue 8038</a>).</li>

1792

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertRaisesRegexp" title="unittest.TestCase.assertRaisesRegexp"><code class="xref py py-meth docutils literal">assertRaisesRegexp()</code></a> checks whether a particular exception

1793

is raised, and then also checks that the string representation of

1794

the exception matches the provided regular expression.</li>

1795

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIn" title="unittest.TestCase.assertIn"><code class="xref py py-meth docutils literal">assertIn()</code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNotIn" title="unittest.TestCase.assertNotIn"><code class="xref py py-meth docutils literal">assertNotIn()</code></a>

1796

tests whether first is or is not in second.</li>

1797

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertItemsEqual" title="unittest.TestCase.assertItemsEqual"><code class="xref py py-meth docutils literal">assertItemsEqual()</code></a> tests whether two provided sequences

1798

contain the same elements.</li>

1799

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertSetEqual" title="unittest.TestCase.assertSetEqual"><code class="xref py py-meth docutils literal">assertSetEqual()</code></a> compares whether two sets are equal, and

1800

only reports the differences between the sets in case of error.</li>

1801

<li>Similarly, <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertListEqual" title="unittest.TestCase.assertListEqual"><code class="xref py py-meth docutils literal">assertListEqual()</code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertTupleEqual" title="unittest.TestCase.assertTupleEqual"><code class="xref py py-meth docutils literal">assertTupleEqual()</code></a>

1802

compare the specified types and explain any differences without necessarily

1803

printing their full values; these methods are now used by default

1804

when comparing lists and tuples using <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal">assertEqual()</code></a>.

1805

More generally, <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertSequenceEqual" title="unittest.TestCase.assertSequenceEqual"><code class="xref py py-meth docutils literal">assertSequenceEqual()</code></a> compares two sequences

1806

and can optionally check whether both sequences are of a

1807

particular type.</li>

1808

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertDictEqual" title="unittest.TestCase.assertDictEqual"><code class="xref py py-meth docutils literal">assertDictEqual()</code></a> compares two dictionaries and reports the

1809

differences; it’s now used by default when you compare two dictionaries

1810

using <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal">assertEqual()</code></a>. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertDictContainsSubset" title="unittest.TestCase.assertDictContainsSubset"><code class="xref py py-meth docutils literal">assertDictContainsSubset()</code></a> checks whether

1811

all of the key/value pairs in first are found in second.</li>

1812

<li><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertAlmostEqual" title="unittest.TestCase.assertAlmostEqual"><code class="xref py py-meth docutils literal">assertAlmostEqual()</code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNotAlmostEqual" title="unittest.TestCase.assertNotAlmostEqual"><code class="xref py py-meth docutils literal">assertNotAlmostEqual()</code></a> test

1813

whether first and second are approximately equal. This method

1814

can either round their difference to an optionally-specified number

1815

of places (the default is 7) and compare it to zero, or require

1816

the difference to be smaller than a supplied delta value.</li>

1817

<li><a class="reference internal" href="../library/unittest.html#unittest.TestLoader.loadTestsFromName" title="unittest.TestLoader.loadTestsFromName"><code class="xref py py-meth docutils literal">loadTestsFromName()</code></a> properly honors the

1818

<a class="reference internal" href="../library/unittest.html#unittest.TestLoader.suiteClass" title="unittest.TestLoader.suiteClass"><code class="xref py py-attr docutils literal">suiteClass</code></a> attribute of

1819

the <a class="reference internal" href="../library/unittest.html#unittest.TestLoader" title="unittest.TestLoader"><code class="xref py py-class docutils literal">TestLoader</code></a>. (Fixed by Mark Roddy; <a class="reference external" href="https://bugs.python.org/issue6866">issue 6866</a>.)</li>

1820

<li>A new hook lets you extend the <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal">assertEqual()</code></a> method to handle

1821

new data types. The <a class="reference internal" href="../library/unittest.html#unittest.TestCase.addTypeEqualityFunc" title="unittest.TestCase.addTypeEqualityFunc"><code class="xref py py-meth docutils literal">addTypeEqualityFunc()</code></a> method takes a type

1822

object and a function. The function will be used when both of the

1823

objects being compared are of the specified type. This function

1824

should compare the two objects and raise an exception if they don’t

1825

match; it’s a good idea for the function to provide additional

1826

information about why the two objects aren’t matching, much as the new

1827

sequence comparison methods do.</li>

1828

</ul>

1829

<a class="reference internal" href="../library/unittest.html#unittest.main" title="unittest.main"><code class="xref py py-func docutils literal">unittest.main()</code></a> now takes an optional <code class="docutils literal">exit</code> argument. If

1830

False, <a class="reference internal" href="../library/unittest.html#unittest.main" title="unittest.main"><code class="xref py py-func docutils literal">main()</code></a> doesn’t call <a class="reference internal" href="../library/sys.html#sys.exit" title="sys.exit"><code class="xref py py-func docutils literal">sys.exit()</code></a>, allowing

1831

<a class="reference internal" href="../library/unittest.html#unittest.main" title="unittest.main"><code class="xref py py-func docutils literal">main()</code></a> to be used from the interactive interpreter.

1832

(Contributed by J. Pablo Fernández; <a class="reference external" href="https://bugs.python.org/issue3379">issue 3379</a>.)

1833

<a class="reference internal" href="../library/unittest.html#unittest.TestResult" title="unittest.TestResult"><code class="xref py py-class docutils literal">TestResult</code></a> has new <a class="reference internal" href="../library/unittest.html#unittest.TestResult.startTestRun" title="unittest.TestResult.startTestRun"><code class="xref py py-meth docutils literal">startTestRun()</code></a> and

1834

<a class="reference internal" href="../library/unittest.html#unittest.TestResult.stopTestRun" title="unittest.TestResult.stopTestRun"><code class="xref py py-meth docutils literal">stopTestRun()</code></a> methods that are called immediately before

1835

and after a test run. (Contributed by Robert Collins; <a class="reference external" href="https://bugs.python.org/issue5728">issue 5728</a>.)

1836

With all these changes, the <code class="file docutils literal">unittest.py</code> was becoming awkwardly

1837

large, so the module was turned into a package and the code split into

1838

several files (by Benjamin Peterson). This doesn’t affect how the

1839

module is imported or used.

1840

1841

See also

1842

1843

<dt><a class="reference external" href="http://www.voidspace.org.uk/python/articles/unittest2.shtml">http://www.voidspace.org.uk/python/articles/unittest2.shtml</a></dt>

1844

<dd>Describes the new features, how to use them, and the

1845

rationale for various design decisions. (By Michael Foord.)</dd>

1846

</dl>

1847

</div>

1848

</div>

1849

1850

<h3>Updated module: ElementTree 1.3<a class="headerlink" href="#updated-module-elementtree-1-3" title="Permalink to this headline">¶</a></h3>

1851

The version of the ElementTree library included with Python was updated to

1852

version 1.3. Some of the new features are:

1853

<ul>

1854

<li>The various parsing functions now take a parser keyword argument

1855

giving an <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.XMLParser" title="xml.etree.ElementTree.XMLParser"><code class="xref py py-class docutils literal">XMLParser</code></a> instance that will

1856

be used. This makes it possible to override the file’s internal encoding:

1857

<div class="highlight-python"><div class="highlight"><pre>p = ET.XMLParser(encoding='utf-8')

1858

t = ET.XML("""<root/>""", parser=p)

1859

</pre></div>

1860

</div>

1861

Errors in parsing XML now raise a <code class="xref py py-exc docutils literal">ParseError</code> exception, whose

1862

instances have a <code class="xref py py-attr docutils literal">position</code> attribute

1863

containing a (line, column) tuple giving the location of the problem.

1864

</li>

1865

<li>ElementTree’s code for converting trees to a string has been

1866

significantly reworked, making it roughly twice as fast in many

1867

cases. The <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.ElementTree.write" title="xml.etree.ElementTree.ElementTree.write"><code class="xref py py-meth docutils literal">ElementTree.write()</code></a>

1868

and <code class="xref py py-meth docutils literal">Element.write()</code> methods now have a method parameter that can be

1869

“xml” (the default), “html”, or “text”. HTML mode will output empty

1870

elements as <code class="docutils literal"><empty></empty></code> instead of <code class="docutils literal"><empty/></code>, and text

1871

mode will skip over elements and only output the text chunks. If

1872

you set the <code class="xref py py-attr docutils literal">tag</code> attribute of an element to <code class="docutils literal">None</code> but

1873

leave its children in place, the element will be omitted when the

1874

tree is written out, so you don’t need to do more extensive rearrangement

1875

to remove a single element.

1876

Namespace handling has also been improved. All <code class="docutils literal">xmlns:<whatever></code>

1877

declarations are now output on the root element, not scattered throughout

1878

the resulting XML. You can set the default namespace for a tree

1879

by setting the <code class="xref py py-attr docutils literal">default_namespace</code> attribute and can

1880

register new prefixes with <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.register_namespace" title="xml.etree.ElementTree.register_namespace"><code class="xref py py-meth docutils literal">register_namespace()</code></a>. In XML mode,

1881

you can use the true/false xml_declaration parameter to suppress the

1882

XML declaration.

1883

</li>

1884

<li>New <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element" title="xml.etree.ElementTree.Element"><code class="xref py py-class docutils literal">Element</code></a> method:

1885

<a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.extend" title="xml.etree.ElementTree.Element.extend"><code class="xref py py-meth docutils literal">extend()</code></a> appends the items from a

1886

sequence to the element’s children. Elements themselves behave like

1887

sequences, so it’s easy to move children from one element to

1888

another:

1889

<div class="highlight-python"><div class="highlight"><pre>from xml.etree import ElementTree as ET

1890

1891

t = ET.XML("""<list>

1892

1893

</list>""")

1894

new = ET.XML('<root/>')

1895

new.extend(t)

1896

1897

# Outputs <root><item>1</item>...</root>

1898

print ET.tostring(new)

1899

</pre></div>

1900

</div>

1901

</li>

1902

<li>New <code class="xref py py-class docutils literal">Element</code> method:

1903

<a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.iter" title="xml.etree.ElementTree.Element.iter"><code class="xref py py-meth docutils literal">iter()</code></a> yields the children of the

1904

element as a generator. It’s also possible to write <code class="docutils literal">for child in

1905

elem:</code> to loop over an element’s children. The existing method

1906

<code class="xref py py-meth docutils literal">getiterator()</code> is now deprecated, as is <code class="xref py py-meth docutils literal">getchildren()</code>

1907

which constructs and returns a list of children.

1908

</li>

1909

<li>New <code class="xref py py-class docutils literal">Element</code> method:

1910

<a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.itertext" title="xml.etree.ElementTree.Element.itertext"><code class="xref py py-meth docutils literal">itertext()</code></a> yields all chunks of

1911

text that are descendants of the element. For example:

1912

1913

1914

</list>""")

1915

1916

# Outputs ['\n ', '1', ' ', '2', ' ', '3', '\n']

1917

print list(t.itertext())

1918

</pre></div>

1919

</div>

1920

</li>

1921

<li>Deprecated: using an element as a Boolean (i.e., <code class="docutils literal">if elem:</code>) would

1922

return true if the element had any children, or false if there were

1923

no children. This behaviour is confusing – <code class="docutils literal">None</code> is false, but

1924

so is a childless element? – so it will now trigger a

1925

<a class="reference internal" href="../library/exceptions.html#exceptions.FutureWarning" title="exceptions.FutureWarning"><code class="xref py py-exc docutils literal">FutureWarning</code></a>. In your code, you should be explicit: write

1926

<code class="docutils literal">len(elem) != 0</code> if you’re interested in the number of children,

1927

or <code class="docutils literal">elem is not None</code>.

1928

</li>

1929

</ul>

1930

Fredrik Lundh develops ElementTree and produced the 1.3 version;

1931

you can read his article describing 1.3 at

1932

<a class="reference external" href="http://effbot.org/zone/elementtree-13-intro.htm">http://effbot.org/zone/elementtree-13-intro.htm</a>.

1933

Florent Xicluna updated the version included with

1934

Python, after discussions on python-dev and in <a class="reference external" href="https://bugs.python.org/issue6472">issue 6472</a>.)

1935

</div>

1936

</div>

1937

1938

<h2>Build and C API Changes<a class="headerlink" href="#build-and-c-api-changes" title="Permalink to this headline">¶</a></h2>

1939

Changes to Python’s build process and to the C API include:

1940

<ul>

1941

<li>The latest release of the GNU Debugger, GDB 7, can be <a class="reference external" href="http://sourceware.org/gdb/current/onlinedocs/gdb/Python.html">scripted

1942

using Python</a>.

1943

When you begin debugging an executable program P, GDB will look for

1944

a file named <code class="docutils literal">P-gdb.py</code> and automatically read it. Dave Malcolm

1945

contributed a <code class="file docutils literal">python-gdb.py</code> that adds a number of

1946

commands useful when debugging Python itself. For example,

1947

<code class="docutils literal">py-up</code> and <code class="docutils literal">py-down</code> go up or down one Python stack frame,

1948

which usually corresponds to several C stack frames. <code class="docutils literal">py-print</code>

1949

prints the value of a Python variable, and <code class="docutils literal">py-bt</code> prints the

1950

Python stack trace. (Added as a result of <a class="reference external" href="https://bugs.python.org/issue8032">issue 8032</a>.)

1951

</li>

1952

<li>If you use the <code class="file docutils literal">.gdbinit</code> file provided with Python,

1953

the “pyo” macro in the 2.7 version now works correctly when the thread being

1954

debugged doesn’t hold the GIL; the macro now acquires it before printing.

1955

(Contributed by Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue3632">issue 3632</a>.)

1956

</li>

1957

<li><a class="reference internal" href="../c-api/init.html#c.Py_AddPendingCall" title="Py_AddPendingCall"><code class="xref c c-func docutils literal">Py_AddPendingCall()</code></a> is now thread-safe, letting any

1958

worker thread submit notifications to the main Python thread. This

1959

is particularly useful for asynchronous IO operations.

1960

(Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue4293">issue 4293</a>.)

1961

</li>

1962

<li>New function: <a class="reference internal" href="../c-api/code.html#c.PyCode_NewEmpty" title="PyCode_NewEmpty"><code class="xref c c-func docutils literal">PyCode_NewEmpty()</code></a> creates an empty code object;

1963

only the filename, function name, and first line number are required.

1964

This is useful for extension modules that are attempting to

1965

construct a more useful traceback stack. Previously such

1966

extensions needed to call <a class="reference internal" href="../c-api/code.html#c.PyCode_New" title="PyCode_New"><code class="xref c c-func docutils literal">PyCode_New()</code></a>, which had many

1967

more arguments. (Added by Jeffrey Yasskin.)

1968

</li>

1969

<li>New function: <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_NewExceptionWithDoc" title="PyErr_NewExceptionWithDoc"><code class="xref c c-func docutils literal">PyErr_NewExceptionWithDoc()</code></a> creates a new

1970

exception class, just as the existing <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_NewException" title="PyErr_NewException"><code class="xref c c-func docutils literal">PyErr_NewException()</code></a> does,

1971

but takes an extra <code class="docutils literal">char *</code> argument containing the docstring for the

1972

new exception class. (Added by ‘lekma’ on the Python bug tracker;

1973

<a class="reference external" href="https://bugs.python.org/issue7033">issue 7033</a>.)

1974

</li>

1975

<li>New function: <a class="reference internal" href="../c-api/reflection.html#c.PyFrame_GetLineNumber" title="PyFrame_GetLineNumber"><code class="xref c c-func docutils literal">PyFrame_GetLineNumber()</code></a> takes a frame object

1976

and returns the line number that the frame is currently executing.

1977

Previously code would need to get the index of the bytecode

1978

instruction currently executing, and then look up the line number

1979

corresponding to that address. (Added by Jeffrey Yasskin.)

1980

</li>

1981

<li>New functions: <a class="reference internal" href="../c-api/long.html#c.PyLong_AsLongAndOverflow" title="PyLong_AsLongAndOverflow"><code class="xref c c-func docutils literal">PyLong_AsLongAndOverflow()</code></a> and

1982

<a class="reference internal" href="../c-api/long.html#c.PyLong_AsLongLongAndOverflow" title="PyLong_AsLongLongAndOverflow"><code class="xref c c-func docutils literal">PyLong_AsLongLongAndOverflow()</code></a> approximates a Python long

1983

integer as a C <code class="xref c c-type docutils literal">long</code> or <code class="xref c c-type docutils literal">long long</code>.

1984

If the number is too large to fit into

1985

the output type, an overflow flag is set and returned to the caller.

1986

(Contributed by Case Van Horsen; <a class="reference external" href="https://bugs.python.org/issue7528">issue 7528</a> and <a class="reference external" href="https://bugs.python.org/issue7767">issue 7767</a>.)

1987

</li>

1988

<li>New function: stemming from the rewrite of string-to-float conversion,

1989

a new <a class="reference internal" href="../c-api/conversion.html#c.PyOS_string_to_double" title="PyOS_string_to_double"><code class="xref c c-func docutils literal">PyOS_string_to_double()</code></a> function was added. The old

1990

<a class="reference internal" href="../c-api/conversion.html#c.PyOS_ascii_strtod" title="PyOS_ascii_strtod"><code class="xref c c-func docutils literal">PyOS_ascii_strtod()</code></a> and <a class="reference internal" href="../c-api/conversion.html#c.PyOS_ascii_atof" title="PyOS_ascii_atof"><code class="xref c c-func docutils literal">PyOS_ascii_atof()</code></a> functions

1991

are now deprecated.

1992

</li>

1993

<li>New function: <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal">PySys_SetArgvEx()</code></a> sets the value of

1994

<code class="docutils literal">sys.argv</code> and can optionally update <code class="docutils literal">sys.path</code> to include the

1995

directory containing the script named by <code class="docutils literal">sys.argv[0]</code> depending

1996

on the value of an updatepath parameter.

1997

This function was added to close a security hole for applications

1998

that embed Python. The old function, <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal">PySys_SetArgv()</code></a>, would

1999

always update <code class="docutils literal">sys.path</code>, and sometimes it would add the current

2000

directory. This meant that, if you ran an application embedding

2001

Python in a directory controlled by someone else, attackers could

2002

put a Trojan-horse module in the directory (say, a file named

2003

<code class="file docutils literal">os.py</code>) that your application would then import and run.

2004

If you maintain a C/C++ application that embeds Python, check

2005

whether you’re calling <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal">PySys_SetArgv()</code></a> and carefully consider

2006

whether the application should be using <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal">PySys_SetArgvEx()</code></a>

2007

with updatepath set to false.

2008

Security issue reported as <a class="reference external" href="http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983">CVE-2008-5983</a>;

2009

discussed in <a class="reference external" href="https://bugs.python.org/issue5753">issue 5753</a>, and fixed by Antoine Pitrou.

2010

</li>

2011

<li>New macros: the Python header files now define the following macros:

2012

<code class="xref c c-macro docutils literal">Py_ISALNUM</code>,

2013

<code class="xref c c-macro docutils literal">Py_ISALPHA</code>,

2014

<code class="xref c c-macro docutils literal">Py_ISDIGIT</code>,

2015

<code class="xref c c-macro docutils literal">Py_ISLOWER</code>,

2016

<code class="xref c c-macro docutils literal">Py_ISSPACE</code>,

2017

<code class="xref c c-macro docutils literal">Py_ISUPPER</code>,

2018

<code class="xref c c-macro docutils literal">Py_ISXDIGIT</code>,

2019

<code class="xref c c-macro docutils literal">Py_TOLOWER</code>, and <code class="xref c c-macro docutils literal">Py_TOUPPER</code>.

2020

All of these functions are analogous to the C

2021

standard macros for classifying characters, but ignore the current

2022

locale setting, because in

2023

several places Python needs to analyze characters in a

2024

locale-independent way. (Added by Eric Smith;

2025

<a class="reference external" href="https://bugs.python.org/issue5793">issue 5793</a>.)

2026

</li>

2027

<li>Removed function: <code class="xref c c-macro docutils literal">PyEval_CallObject</code> is now only available

2028

as a macro. A function version was being kept around to preserve

2029

ABI linking compatibility, but that was in 1997; it can certainly be

2030

deleted by now. (Removed by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue8276">issue 8276</a>.)

2031

</li>

2032

<li>New format codes: the <code class="xref c c-func docutils literal">PyFormat_FromString()</code>,

2033

<code class="xref c c-func docutils literal">PyFormat_FromStringV()</code>, and <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_Format" title="PyErr_Format"><code class="xref c c-func docutils literal">PyErr_Format()</code></a> functions now

2034

accept <code class="docutils literal">%lld</code> and <code class="docutils literal">%llu</code> format codes for displaying

2035

C’s <code class="xref c c-type docutils literal">long long</code> types.

2036

(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue7228">issue 7228</a>.)

2037

</li>

2038

<li>The complicated interaction between threads and process forking has

2039

been changed. Previously, the child process created by

2040

<a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal">os.fork()</code></a> might fail because the child is created with only a

2041

single thread running, the thread performing the <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal">os.fork()</code></a>.

2042

If other threads were holding a lock, such as Python’s import lock,

2043

when the fork was performed, the lock would still be marked as

2044

“held” in the new process. But in the child process nothing would

2045

ever release the lock, since the other threads weren’t replicated,

2046

and the child process would no longer be able to perform imports.

2047

Python 2.7 acquires the import lock before performing an

2048

<a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal">os.fork()</code></a>, and will also clean up any locks created using the

2049

<a class="reference internal" href="../library/threading.html#module-threading" title="threading: Higher-level threading interface."><code class="xref py py-mod docutils literal">threading</code></a> module. C extension modules that have internal

2050

locks, or that call <code class="xref c c-func docutils literal">fork()</code> themselves, will not benefit

2051

from this clean-up.

2052

(Fixed by Thomas Wouters; <a class="reference external" href="https://bugs.python.org/issue1590864">issue 1590864</a>.)

2053

</li>

2054

<li>The <a class="reference internal" href="../c-api/init.html#c.Py_Finalize" title="Py_Finalize"><code class="xref c c-func docutils literal">Py_Finalize()</code></a> function now calls the internal

2055

<code class="xref py py-func docutils literal">threading._shutdown()</code> function; this prevents some exceptions from

2056

being raised when an interpreter shuts down.

2057

(Patch by Adam Olsen; <a class="reference external" href="https://bugs.python.org/issue1722344">issue 1722344</a>.)

2058

</li>

2059

<li>When using the <a class="reference internal" href="../c-api/structures.html#c.PyMemberDef" title="PyMemberDef"><code class="xref c c-type docutils literal">PyMemberDef</code></a> structure to define attributes

2060

of a type, Python will no longer let you try to delete or set a

2061

<code class="xref py py-const docutils literal">T_STRING_INPLACE</code> attribute.

2062

</li>

2063

<li>Global symbols defined by the <a class="reference internal" href="../library/ctypes.html#module-ctypes" title="ctypes: A foreign function library for Python."><code class="xref py py-mod docutils literal">ctypes</code></a> module are now prefixed

2064

with <code class="docutils literal">Py</code>, or with <code class="docutils literal">_ctypes</code>. (Implemented by Thomas

2065

Heller; <a class="reference external" href="https://bugs.python.org/issue3102">issue 3102</a>.)

2066

</li>

2067

<li>New configure option: the <code class="xref std std-option docutils literal">--with-system-expat</code> switch allows

2068

building the <code class="xref py py-mod docutils literal">pyexpat</code> module to use the system Expat library.

2069

(Contributed by Arfrever Frehtes Taifersar Arahesis; <a class="reference external" href="https://bugs.python.org/issue7609">issue 7609</a>.)

2070

</li>

2071

<li>New configure option: the

2072

<code class="xref std std-option docutils literal">--with-valgrind</code> option will now disable the pymalloc

2073

allocator, which is difficult for the Valgrind memory-error detector

2074

to analyze correctly.

2075

Valgrind will therefore be better at detecting memory leaks and

2076

overruns. (Contributed by James Henstridge; <a class="reference external" href="https://bugs.python.org/issue2422">issue 2422</a>.)

2077

</li>

2078

<li>New configure option: you can now supply an empty string to

2079

<code class="xref std std-option docutils literal">--with-dbmliborder=</code> in order to disable all of the various

2080

DBM modules. (Added by Arfrever Frehtes Taifersar Arahesis;

2081

<a class="reference external" href="https://bugs.python.org/issue6491">issue 6491</a>.)

2082

</li>

2083

<li>The configure script now checks for floating-point rounding bugs

2084

on certain 32-bit Intel chips and defines a <code class="xref c c-macro docutils literal">X87_DOUBLE_ROUNDING</code>

2085

preprocessor definition. No code currently uses this definition,

2086

but it’s available if anyone wishes to use it.

2087

(Added by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue2937">issue 2937</a>.)

2088

configure also now sets a <code class="xref std std-envvar docutils literal">LDCXXSHARED</code> Makefile

2089

variable for supporting C++ linking. (Contributed by Arfrever

2090

Frehtes Taifersar Arahesis; <a class="reference external" href="https://bugs.python.org/issue1222585">issue 1222585</a>.)

2091

</li>

2092

<li>The build process now creates the necessary files for pkg-config

2093

support. (Contributed by Clinton Roy; <a class="reference external" href="https://bugs.python.org/issue3585">issue 3585</a>.)

2094

</li>

2095

<li>The build process now supports Subversion 1.7. (Contributed by

2096

Arfrever Frehtes Taifersar Arahesis; <a class="reference external" href="https://bugs.python.org/issue6094">issue 6094</a>.)

2097

</li>

2098

</ul>

2099

2100

<h3>Capsules<a class="headerlink" href="#capsules" title="Permalink to this headline">¶</a></h3>

2101

Python 3.1 adds a new C datatype, <a class="reference internal" href="../c-api/capsule.html#c.PyCapsule" title="PyCapsule"><code class="xref c c-type docutils literal">PyCapsule</code></a>, for providing a

2102

C API to an extension module. A capsule is essentially the holder of

2103

a C <code class="docutils literal">void *</code> pointer, and is made available as a module attribute; for

2104

example, the <a class="reference internal" href="../library/socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal">socket</code></a> module’s API is exposed as <code class="docutils literal">socket.CAPI</code>,

2105

and <a class="reference internal" href="../library/unicodedata.html#module-unicodedata" title="unicodedata: Access the Unicode Database."><code class="xref py py-mod docutils literal">unicodedata</code></a> exposes <code class="docutils literal">ucnhash_CAPI</code>. Other extensions

2106

can import the module, access its dictionary to get the capsule

2107

object, and then get the <code class="docutils literal">void *</code> pointer, which will usually point

2108

to an array of pointers to the module’s various API functions.

2109

There is an existing data type already used for this,

2110

<a class="reference internal" href="../c-api/cobject.html#c.PyCObject" title="PyCObject"><code class="xref c c-type docutils literal">PyCObject</code></a>, but it doesn’t provide type safety. Evil code

2111

written in pure Python could cause a segmentation fault by taking a

2112

2113

2114

and getting the pointer requires providing the name:

2115

<div class="highlight-python"><div class="highlight"><pre>void *vtable;

2116

2117

if (!PyCapsule_IsValid(capsule, "mymodule.CAPI") {

2118

PyErr_SetString(PyExc_ValueError, "argument type invalid");

2119

return NULL;

2120

}

2121

2122

vtable = PyCapsule_GetPointer(capsule, "mymodule.CAPI");

2123

</pre></div>

2124

</div>

2125

You are assured that <code class="docutils literal">vtable</code> points to whatever you’re expecting.

2126

If a different capsule was passed in, <a class="reference internal" href="../c-api/capsule.html#c.PyCapsule_IsValid" title="PyCapsule_IsValid"><code class="xref c c-func docutils literal">PyCapsule_IsValid()</code></a> would

2127

detect the mismatched name and return false. Refer to

2128

<a class="reference internal" href="../extending/extending.html#using-capsules">Providing a C API for an Extension Module</a> for more information on using these objects.

2129

Python 2.7 now uses capsules internally to provide various

2130

extension-module APIs, but the <a class="reference internal" href="../c-api/cobject.html#c.PyCObject_AsVoidPtr" title="PyCObject_AsVoidPtr"><code class="xref c c-func docutils literal">PyCObject_AsVoidPtr()</code></a> was

2131

modified to handle capsules, preserving compile-time compatibility

2132

with the <code class="xref c c-type docutils literal">CObject</code> interface. Use of

2133

<a class="reference internal" href="../c-api/cobject.html#c.PyCObject_AsVoidPtr" title="PyCObject_AsVoidPtr"><code class="xref c c-func docutils literal">PyCObject_AsVoidPtr()</code></a> will signal a

2134

<a class="reference internal" href="../library/exceptions.html#exceptions.PendingDeprecationWarning" title="exceptions.PendingDeprecationWarning"><code class="xref py py-exc docutils literal">PendingDeprecationWarning</code></a>, which is silent by default.

2135

Implemented in Python 3.1 and backported to 2.7 by Larry Hastings;

2136

discussed in <a class="reference external" href="https://bugs.python.org/issue5630">issue 5630</a>.

2137

</div>

2138

2139

<h3>Port-Specific Changes: Windows<a class="headerlink" href="#port-specific-changes-windows" title="Permalink to this headline">¶</a></h3>

2140

2141

<li>The <a class="reference internal" href="../library/msvcrt.html#module-msvcrt" title="msvcrt: Miscellaneous useful routines from the MS VC++ runtime. (Windows)"><code class="xref py py-mod docutils literal">msvcrt</code></a> module now contains some constants from

2142

the <code class="file docutils literal">crtassem.h</code> header file:

2143

<code class="xref py py-data docutils literal">CRT_ASSEMBLY_VERSION</code>,

2144

<code class="xref py py-data docutils literal">VC_ASSEMBLY_PUBLICKEYTOKEN</code>,

2145

and <code class="xref py py-data docutils literal">LIBRARIES_ASSEMBLY_NAME_PREFIX</code>.

2146

(Contributed by David Cournapeau; <a class="reference external" href="https://bugs.python.org/issue4365">issue 4365</a>.)</li>

2147

<li>The <a class="reference internal" href="../library/_winreg.html#module-_winreg" title="_winreg: Routines and objects for manipulating the Windows registry. (Windows)"><code class="xref py py-mod docutils literal">_winreg</code></a> module for accessing the registry now implements

2148

the <a class="reference internal" href="../library/_winreg.html#_winreg.CreateKeyEx" title="_winreg.CreateKeyEx"><code class="xref py py-func docutils literal">CreateKeyEx()</code></a> and <a class="reference internal" href="../library/_winreg.html#_winreg.DeleteKeyEx" title="_winreg.DeleteKeyEx"><code class="xref py py-func docutils literal">DeleteKeyEx()</code></a>

2149

functions, extended versions of previously-supported functions that

2150

take several extra arguments. The <a class="reference internal" href="../library/_winreg.html#_winreg.DisableReflectionKey" title="_winreg.DisableReflectionKey"><code class="xref py py-func docutils literal">DisableReflectionKey()</code></a>,

2151

<a class="reference internal" href="../library/_winreg.html#_winreg.EnableReflectionKey" title="_winreg.EnableReflectionKey"><code class="xref py py-func docutils literal">EnableReflectionKey()</code></a>, and <a class="reference internal" href="../library/_winreg.html#_winreg.QueryReflectionKey" title="_winreg.QueryReflectionKey"><code class="xref py py-func docutils literal">QueryReflectionKey()</code></a>

2152

were also tested and documented.

2153

(Implemented by Brian Curtin: <a class="reference external" href="https://bugs.python.org/issue7347">issue 7347</a>.)</li>

2154

<li>The new <code class="xref c c-func docutils literal">_beginthreadex()</code> API is used to start threads, and

2155

the native thread-local storage functions are now used.

2156

(Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue3582">issue 3582</a>.)</li>

2157

<li>The <a class="reference internal" href="../library/os.html#os.kill" title="os.kill"><code class="xref py py-func docutils literal">os.kill()</code></a> function now works on Windows. The signal value

2158

can be the constants <code class="xref py py-const docutils literal">CTRL_C_EVENT</code>,

2159

<code class="xref py py-const docutils literal">CTRL_BREAK_EVENT</code>, or any integer. The first two constants

2160

will send <code class="kbd docutils literal">Control-C</code> and <code class="kbd docutils literal">Control-Break</code> keystroke events to

2161

subprocesses; any other value will use the <code class="xref c c-func docutils literal">TerminateProcess()</code>

2162

API. (Contributed by Miki Tebeka; <a class="reference external" href="https://bugs.python.org/issue1220212">issue 1220212</a>.)</li>

2163

<li>The <a class="reference internal" href="../library/os.html#os.listdir" title="os.listdir"><code class="xref py py-func docutils literal">os.listdir()</code></a> function now correctly fails

2164

for an empty path. (Fixed by Hirokazu Yamamoto; <a class="reference external" href="https://bugs.python.org/issue5913">issue 5913</a>.)</li>

2165

<li>The <code class="xref py py-mod docutils literal">mimelib</code> module will now read the MIME database from

2166

the Windows registry when initializing.

2167

(Patch by Gabriel Genellina; <a class="reference external" href="https://bugs.python.org/issue4969">issue 4969</a>.)</li>

2168

</ul>

2169

</div>

2170

2171

<h3>Port-Specific Changes: Mac OS X<a class="headerlink" href="#port-specific-changes-mac-os-x" title="Permalink to this headline">¶</a></h3>

2172

2173

<li>The path <code class="docutils literal">/Library/Python/2.7/site-packages</code> is now appended to

2174

<code class="docutils literal">sys.path</code>, in order to share added packages between the system

2175

installation and a user-installed copy of the same version.

2176

(Changed by Ronald Oussoren; <a class="reference external" href="https://bugs.python.org/issue4865">issue 4865</a>.)</li>

2177

</ul>

2178

</div>

2179

2180

<h3>Port-Specific Changes: FreeBSD<a class="headerlink" href="#port-specific-changes-freebsd" title="Permalink to this headline">¶</a></h3>

2181

2182

<li>FreeBSD 7.1’s <code class="xref py py-const docutils literal">SO_SETFIB</code> constant, used with

2183

<code class="xref py py-func docutils literal">getsockopt()</code>/<code class="xref py py-func docutils literal">setsockopt()</code> to select an

2184

alternate routing table, is now available in the <a class="reference internal" href="../library/socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal">socket</code></a>

2185

module. (Added by Kyle VanderBeek; <a class="reference external" href="https://bugs.python.org/issue8235">issue 8235</a>.)</li>

2186

</ul>

2187

</div>

2188

</div>

2189

2190

<h2>Other Changes and Fixes<a class="headerlink" href="#other-changes-and-fixes" title="Permalink to this headline">¶</a></h2>

2191

2192

<li>Two benchmark scripts, <code class="file docutils literal">iobench</code> and <code class="file docutils literal">ccbench</code>, were

2193

added to the <code class="file docutils literal">Tools</code> directory. <code class="file docutils literal">iobench</code> measures the

2194

speed of the built-in file I/O objects returned by <a class="reference internal" href="../library/functions.html#open" title="open"><code class="xref py py-func docutils literal">open()</code></a>

2195

while performing various operations, and <code class="file docutils literal">ccbench</code> is a

2196

concurrency benchmark that tries to measure computing throughput,

2197

thread switching latency, and IO processing bandwidth when

2198

performing several tasks using a varying number of threads.</li>

2199

<li>The <code class="file docutils literal">Tools/i18n/msgfmt.py</code> script now understands plural

2200

forms in <code class="file docutils literal">.po</code> files. (Fixed by Martin von Löwis;

2201

<a class="reference external" href="https://bugs.python.org/issue5464">issue 5464</a>.)</li>

2202

<li>When importing a module from a <code class="file docutils literal">.pyc</code> or <code class="file docutils literal">.pyo</code> file

2203

with an existing <code class="file docutils literal">.py</code> counterpart, the <code class="xref py py-attr docutils literal">co_filename</code>

2204

attributes of the resulting code objects are overwritten when the

2205

original filename is obsolete. This can happen if the file has been

2206

renamed, moved, or is accessed through different paths. (Patch by

2207

Ziga Seilnacht and Jean-Paul Calderone; <a class="reference external" href="https://bugs.python.org/issue1180193">issue 1180193</a>.)</li>

2208

<li>The <code class="file docutils literal">regrtest.py</code> script now takes a <code class="xref std std-option docutils literal">--randseed=</code>

2209

switch that takes an integer that will be used as the random seed

2210

for the <code class="xref std std-option docutils literal">-r</code> option that executes tests in random order.

2211

The <code class="xref std std-option docutils literal">-r</code> option also reports the seed that was used

2212

(Added by Collin Winter.)</li>

2213

<li>Another <code class="file docutils literal">regrtest.py</code> switch is <code class="xref std std-option docutils literal">-j</code>, which

2214

takes an integer specifying how many tests run in parallel. This

2215

allows reducing the total runtime on multi-core machines.

2216

This option is compatible with several other options, including the

2217

<a class="reference internal" href="../using/cmdline.html#cmdoption-R"><code class="xref std std-option docutils literal">-R</code></a> switch which is known to produce long runtimes.

2218

(Added by Antoine Pitrou, <a class="reference external" href="https://bugs.python.org/issue6152">issue 6152</a>.) This can also be used

2219

with a new <code class="xref std std-option docutils literal">-F</code> switch that runs selected tests in a loop

2220

until they fail. (Added by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue7312">issue 7312</a>.)</li>

2221

<li>When executed as a script, the <code class="file docutils literal">py_compile.py</code> module now

2222

accepts <code class="docutils literal">'-'</code> as an argument, which will read standard input for

2223

the list of filenames to be compiled. (Contributed by Piotr

2224

Ożarowski; <a class="reference external" href="https://bugs.python.org/issue8233">issue 8233</a>.)</li>

2225

</ul>

2226

</div>

2227

2228

<h2>Porting to Python 2.7<a class="headerlink" href="#porting-to-python-2-7" title="Permalink to this headline">¶</a></h2>

2229

This section lists previously described changes and other bugfixes

2230

that may require changes to your code:

2231

2232

<li>The <a class="reference internal" href="../library/functions.html#range" title="range"><code class="xref py py-func docutils literal">range()</code></a> function processes its arguments more

2233

consistently; it will now call <a class="reference internal" href="../reference/datamodel.html#object.__int__" title="object.__int__"><code class="xref py py-meth docutils literal">__int__()</code></a> on non-float,

2234

non-integer arguments that are supplied to it. (Fixed by Alexander

2235

Belopolsky; <a class="reference external" href="https://bugs.python.org/issue1533">issue 1533</a>.)</li>

2236

<li>The string <a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-meth docutils literal">format()</code></a> method changed the default precision used

2237

for floating-point and complex numbers from 6 decimal

2238

places to 12, which matches the precision used by <a class="reference internal" href="../library/functions.html#str" title="str"><code class="xref py py-func docutils literal">str()</code></a>.

2239

(Changed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue5920">issue 5920</a>.)</li>

2240

<li>Because of an optimization for the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal">with</code></a> statement, the special

2241

methods <a class="reference internal" href="../reference/datamodel.html#object.__enter__" title="object.__enter__"><code class="xref py py-meth docutils literal">__enter__()</code></a> and <a class="reference internal" href="../reference/datamodel.html#object.__exit__" title="object.__exit__"><code class="xref py py-meth docutils literal">__exit__()</code></a> must belong to the object’s

2242

type, and cannot be directly attached to the object’s instance. This

2243

affects new-style classes (derived from <a class="reference internal" href="../library/functions.html#object" title="object"><code class="xref py py-class docutils literal">object</code></a>) and C extension

2244

types. (<a class="reference external" href="https://bugs.python.org/issue6101">issue 6101</a>.)</li>

2245

<li>Due to a bug in Python 2.6, the exc_value parameter to

2246

2247

exception, not an instance. This was fixed in 2.7, so exc_value

2248

will be an instance as expected. (Fixed by Florent Xicluna;

2249

<a class="reference external" href="https://bugs.python.org/issue7853">issue 7853</a>.)</li>

2250

<li>When a restricted set of attributes were set using <code class="docutils literal">__slots__</code>,

2251

2252

as you would expect. Fixed by Benjamin Peterson; <a class="reference external" href="https://bugs.python.org/issue7604">issue 7604</a>.)</li>

2253

</ul>

2254

In the standard library:

2255

<ul>

2256

<li>Operations with <a class="reference internal" href="../library/datetime.html#datetime.datetime" title="datetime.datetime"><code class="xref py py-class docutils literal">datetime</code></a> instances that resulted in a year

2257

falling outside the supported range didn’t always raise

2258

<a class="reference internal" href="../library/exceptions.html#exceptions.OverflowError" title="exceptions.OverflowError"><code class="xref py py-exc docutils literal">OverflowError</code></a>. Such errors are now checked more carefully

2259

and will now raise the exception. (Reported by Mark Leander, patch

2260

by Anand B. Pillai and Alexander Belopolsky; <a class="reference external" href="https://bugs.python.org/issue7150">issue 7150</a>.)

2261

</li>

2262

<li>When using <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal">Decimal</code></a> instances with a string’s

2263

<a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-meth docutils literal">format()</code></a> method, the default alignment was previously

2264

left-alignment. This has been changed to right-alignment, which might

2265

change the output of your programs.

2266

(Changed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue6857">issue 6857</a>.)

2267

Comparisons involving a signaling NaN value (or <code class="docutils literal">sNAN</code>) now signal

2268

<a class="reference internal" href="../library/decimal.html#decimal.InvalidOperation" title="decimal.InvalidOperation"><code class="xref py py-const docutils literal">InvalidOperation</code></a> instead of silently returning a true or

2269

false value depending on the comparison operator. Quiet NaN values

2270

(or <code class="docutils literal">NaN</code>) are now hashable. (Fixed by Mark Dickinson;

2271

<a class="reference external" href="https://bugs.python.org/issue7279">issue 7279</a>.)

2272

</li>

2273

<li>The ElementTree library, <code class="xref py py-mod docutils literal">xml.etree</code>, no longer escapes

2274

ampersands and angle brackets when outputting an XML processing

2275

instruction (which looks like <cite><?xml-stylesheet href=”#style1”?></cite>)

2276

or comment (which looks like <cite><!– comment –></cite>).

2277

(Patch by Neil Muller; <a class="reference external" href="https://bugs.python.org/issue2746">issue 2746</a>.)

2278

</li>

2279

<li>The <code class="xref py py-meth docutils literal">readline()</code> method of <a class="reference internal" href="../library/stringio.html#StringIO.StringIO" title="StringIO.StringIO"><code class="xref py py-class docutils literal">StringIO</code></a> objects now does

2280

nothing when a negative length is requested, as other file-like

2281

objects do. (<a class="reference external" href="https://bugs.python.org/issue7348">issue 7348</a>).

2282

</li>

2283

2284

identifier instead of the previous default value of <code class="docutils literal">'python'</code>.

2285

(Changed by Sean Reifschneider; <a class="reference external" href="https://bugs.python.org/issue8451">issue 8451</a>.)

2286

</li>

2287

2288

no longer suppress fatal errors. The default error level was previously 0,

2289

which meant that errors would only result in a message being written to the

2290

debug log, but because the debug log is not activated by default,

2291

these errors go unnoticed. The default error level is now 1,

2292

which raises an exception if there’s an error.

2293

(Changed by Lars Gustäbel; <a class="reference external" href="https://bugs.python.org/issue7357">issue 7357</a>.)

2294

</li>

2295

2296

unknown URL schemes in a fashion compliant with <a class="rfc reference external" href="https://tools.ietf.org/html/rfc3986.html">RFC 3986</a>: if the

2297

URL is of the form <code class="docutils literal">"<something>://..."</code>, the text before the

2298

<code class="docutils literal">://</code> is treated as the scheme, even if it’s a made-up scheme that

2299

the module doesn’t know about. This change may break code that

2300

worked around the old behaviour. For example, Python 2.6.4 or 2.5

2301

will return the following:

2302

<div class="highlight-python"><div class="highlight"><pre>>>> import urlparse

2303

2304

('invented', '', '//host/filename?query', '', '')

2305

</pre></div>

2306

</div>

2307

Python 2.7 (and Python 2.6.5) will return:

2308

<div class="highlight-python"><div class="highlight"><pre>>>> import urlparse

2309

2310

('invented', 'host', '/filename?query', '', '')

2311

</pre></div>

2312

</div>

2313

(Python 2.7 actually produces slightly different output, since it

2314

returns a named tuple instead of a standard tuple.)

2315

</li>

2316

</ul>

2317

For C extensions:

2318

2319

<li>C extensions that use integer format codes with the <code class="docutils literal">PyArg_Parse*</code>

2320

family of functions will now raise a <a class="reference internal" href="../library/exceptions.html#exceptions.TypeError" title="exceptions.TypeError"><code class="xref py py-exc docutils literal">TypeError</code></a> exception

2321

instead of triggering a <a class="reference internal" href="../library/exceptions.html#exceptions.DeprecationWarning" title="exceptions.DeprecationWarning"><code class="xref py py-exc docutils literal">DeprecationWarning</code></a> (<a class="reference external" href="https://bugs.python.org/issue5080">issue 5080</a>).</li>

2322

<li>Use the new <a class="reference internal" href="../c-api/conversion.html#c.PyOS_string_to_double" title="PyOS_string_to_double"><code class="xref c c-func docutils literal">PyOS_string_to_double()</code></a> function instead of the old

2323

2324

which are now deprecated.</li>

2325

</ul>

2326

For applications that embed Python:

2327

2328

<li>The <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal">PySys_SetArgvEx()</code></a> function was added, letting

2329

applications close a security hole when the existing

2330

<a class="reference internal" href="../c-api/init.html#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal">PySys_SetArgv()</code></a> function was used. Check whether you’re

2331

calling <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal">PySys_SetArgv()</code></a> and carefully consider whether the

2332

application should be using <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal">PySys_SetArgvEx()</code></a> with

2333

updatepath set to false.</li>

2334

</ul>

2335

</div>

2336

2337

<h2>New Features Added to Python 2.7 Maintenance Releases<a class="headerlink" href="#new-features-added-to-python-2-7-maintenance-releases" title="Permalink to this headline">¶</a></h2>

2338

New features may be added to Python 2.7 maintenance releases when the

2339

situation genuinely calls for it. Any such additions must go through

2340

the Python Enhancement Proposal process, and make a compelling case for why

2341

they can’t be adequately addressed by either adding the new feature solely to

2342

Python 3, or else by publishing it on the Python Package Index.

2343

In addition to the specific proposals listed below, there is a general

2344

exemption allowing new <code class="docutils literal">-3</code> warnings to be added in any Python 2.7

2345

maintenance release.

2346

2347

<h3>PEP 434: IDLE Enhancement Exception for All Branches<a class="headerlink" href="#pep-434-idle-enhancement-exception-for-all-branches" title="Permalink to this headline">¶</a></h3>

2348

<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0434">PEP 434</a> describes a general exemption for changes made to the IDLE

2349

development environment shipped along with Python. This exemption makes it

2350

possible for the IDLE developers to provide a more consistent user

2351

experience across all supported versions of Python 2 and 3.

2352

For details of any IDLE changes, refer to the NEWS file for the specific

2353

release.

2354

</div>

2355

2356

<h3>PEP 466: Network Security Enhancements for Python 2.7<a class="headerlink" href="#pep-466-network-security-enhancements-for-python-2-7" title="Permalink to this headline">¶</a></h3>

2357

<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0466">PEP 466</a> describes a number of network security enhancement proposals

2358

that have been approved for inclusion in Python 2.7 maintenance releases,

2359

with the first of those changes appearing in the Python 2.7.7 release.

2360

<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0466">PEP 466</a> related features added in Python 2.7.7:

2361

2362

<li><a class="reference internal" href="../library/hmac.html#hmac.compare_digest" title="hmac.compare_digest"><code class="xref py py-func docutils literal">hmac.compare_digest()</code></a> was backported from Python 3 to make a timing

2363

attack resistant comparison operation available to Python 2 applications.

2364

(Contributed by Alex Gaynor; <a class="reference external" href="https://bugs.python.org/issue21306">issue 21306</a>.)</li>

2365

<li>OpenSSL 1.0.1g was upgraded in the official Windows installers published on

2366

python.org. (Contributed by Zachary Ware; <a class="reference external" href="https://bugs.python.org/issue21462">issue 21462</a>.)</li>

2367

</ul>

2368

<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0466">PEP 466</a> related features added in Python 2.7.8:

2369

2370

<li><a class="reference internal" href="../library/hashlib.html#hashlib.pbkdf2_hmac" title="hashlib.pbkdf2_hmac"><code class="xref py py-func docutils literal">hashlib.pbkdf2_hmac()</code></a> was backported from Python 3 to make a hashing

2371

algorithm suitable for secure password storage broadly available to Python

2372

2 applications. (Contributed by Alex Gaynor; <a class="reference external" href="https://bugs.python.org/issue21304">issue 21304</a>.)</li>

2373

<li>OpenSSL 1.0.1h was upgraded for the official Windows installers published on

2374

python.org. (contributed by Zachary Ware in <a class="reference external" href="https://bugs.python.org/issue21671">issue 21671</a> for CVE-2014-0224)</li>

2375

</ul>

2376

<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0466">PEP 466</a> related features added in Python 2.7.9:

2377

<ul>

2378

<li>Most of Python 3.4’s <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal">ssl</code></a> module was backported. This means <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal">ssl</code></a>

2379

now supports Server Name Indication, TLS1.x settings, access to the platform

2380

certificate store, the <a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal">SSLContext</code></a> class, and other

2381

features. (Contributed by Alex Gaynor and David Reid; <a class="reference external" href="https://bugs.python.org/issue21308">issue 21308</a>.)

2382

Refer to the “Version added: 2.7.9” notes in the module documentation for

2383

specific details.

2384

</li>

2385

<li><a class="reference internal" href="../library/os.html#os.urandom" title="os.urandom"><code class="xref py py-func docutils literal">os.urandom()</code></a> was changed to cache a file descriptor to <code class="docutils literal">/dev/urandom</code>

2386

instead of reopening <code class="docutils literal">/dev/urandom</code> on every call. (Contributed by Alex

2387

Gaynor; <a class="reference external" href="https://bugs.python.org/issue21305">issue 21305</a>.)

2388

</li>

2389

<li><a class="reference internal" href="../library/hashlib.html#hashlib.algorithms_guaranteed" title="hashlib.algorithms_guaranteed"><code class="xref py py-data docutils literal">hashlib.algorithms_guaranteed</code></a> and

2390

<a class="reference internal" href="../library/hashlib.html#hashlib.algorithms_available" title="hashlib.algorithms_available"><code class="xref py py-data docutils literal">hashlib.algorithms_available</code></a> were backported from Python 3 to make

2391

it easier for Python 2 applications to select the strongest available hash

2392

algorithm. (Contributed by Alex Gaynor in <a class="reference external" href="https://bugs.python.org/issue21307">issue 21307</a>)

2393

</li>

2394

</ul>

2395

</div>

2396

2397

<h3>PEP 477: Backport ensurepip (PEP 453) to Python 2.7<a class="headerlink" href="#pep-477-backport-ensurepip-pep-453-to-python-2-7" title="Permalink to this headline">¶</a></h3>

2398

<a class="pep reference external" href="https://www.python.org/dev/peps/pep-0477">PEP 477</a> approves the inclusion of the <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0453">PEP 453</a> ensurepip module and the

2399

improved documentation that was enabled by it in the Python 2.7 maintenance

2400

releases, appearing first in the the Python 2.7.9 release.

2401

2402

<h4>Bootstrapping pip By Default<a class="headerlink" href="#bootstrapping-pip-by-default" title="Permalink to this headline">¶</a></h4>

2403

The new <a class="reference internal" href="../library/ensurepip.html#module-ensurepip" title="ensurepip: Bootstrapping the ``pip`` installer into an existing Python installation or virtual environment."><code class="xref py py-mod docutils literal">ensurepip</code></a> module (defined in <a class="pep reference external" href="https://www.python.org/dev/peps/pep-0453">PEP 453</a>) provides a standard

2404

cross-platform mechanism to bootstrap the pip installer into Python

2405

installations. The version of <code class="docutils literal">pip</code> included with Python 2.7.9 is <code class="docutils literal">pip</code>

2406

1.5.6, and future 2.7.x maintenance releases will update the bundled version to

2407

the latest version of <code class="docutils literal">pip</code> that is available at the time of creating the

2408

release candidate.

2409

By default, the commands <code class="docutils literal">pip</code>, <code class="docutils literal">pipX</code> and <code class="docutils literal">pipX.Y</code> will be installed on

2410

all platforms (where X.Y stands for the version of the Python installation),

2411

along with the <code class="docutils literal">pip</code> Python package and its dependencies.

2412

For CPython <a class="reference internal" href="../using/unix.html#building-python-on-unix">source builds on POSIX systems</a>,

2413

the <code class="docutils literal">make install</code> and <code class="docutils literal">make altinstall</code> commands do not bootstrap <code class="docutils literal">pip</code>

2414

by default. This behaviour can be controlled through configure options, and

2415

overridden through Makefile options.

2416

On Windows and Mac OS X, the CPython installers now default to installing

2417

<code class="docutils literal">pip</code> along with CPython itself (users may opt out of installing it

2418

during the installation process). Window users will need to opt in to the

2419

automatic <code class="docutils literal">PATH</code> modifications to have <code class="docutils literal">pip</code> available from the command

2420

line by default, otherwise it can still be accessed through the Python

2421

launcher for Windows as <code class="docutils literal">py -m pip</code>.

2422

As <a class="reference external" href="https://www.python.org/dev/peps/pep-0477/#disabling-ensurepip-by-downstream-distributors">discussed in the PEP</a>, platform packagers may choose not to install

2423

these commands by default, as long as, when invoked, they provide clear and

2424

simple directions on how to install them on that platform (usually using

2425

the system package manager).

2426

</div>

2427

2428

<h4>Documentation Changes<a class="headerlink" href="#documentation-changes" title="Permalink to this headline">¶</a></h4>

2429

As part of this change, the <a class="reference internal" href="../installing/index.html#installing-index">Installing Python Modules</a> and

2430

<a class="reference internal" href="../distributing/index.html#distributing-index">Distributing Python Modules</a> sections of the documentation have been

2431

completely redesigned as short getting started and FAQ documents. Most

2432

packaging documentation has now been moved out to the Python Packaging

2433

Authority maintained <a class="reference external" href="http://packaging.python.org">Python Packaging User Guide</a> and the documentation of the individual

2434

projects.

2435

However, as this migration is currently still incomplete, the legacy

2436

versions of those guides remaining available as <a class="reference internal" href="../install/index.html#install-index">Installing Python Modules</a>

2437

and <a class="reference internal" href="../distutils/index.html#distutils-index">Distributing Python Modules</a>.

2438

2439

See also

2440

2441

<dt><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0453">PEP 453</a> – Explicit bootstrapping of pip in Python installations</dt>

2442

<dd>PEP written by Donald Stufft and Nick Coghlan, implemented by

2443

Donald Stufft, Nick Coghlan, Martin von Löwis and Ned Deily.</dd>

2444

</dl>

2445

</div>

2446

</div>

2447

</div>

2448

2449

<h3>PEP 476: Enabling certificate verification by default for stdlib http clients<a class="headerlink" href="#pep-476-enabling-certificate-verification-by-default-for-stdlib-http-clients" title="Permalink to this headline">¶</a></h3>

2450

<a class="reference internal" href="../library/httplib.html#module-httplib" title="httplib: HTTP and HTTPS protocol client (requires sockets)."><code class="xref py py-mod docutils literal">httplib</code></a> and modules which use it, such as <a class="reference internal" href="../library/urllib2.html#module-urllib2" title="urllib2: Next generation URL opening library."><code class="xref py py-mod docutils literal">urllib2</code></a> and

2451

<a class="reference internal" href="../library/xmlrpclib.html#module-xmlrpclib" title="xmlrpclib: XML-RPC client access."><code class="xref py py-mod docutils literal">xmlrpclib</code></a>, will now verify that the server presents a certificate

2452

which is signed by a CA in the platform trust store and whose hostname matches

2453

the hostname being requested by default, significantly improving security for

2454

many applications.

2455

For applications which require the old previous behavior, they can pass an

2456

alternate context:

2457

<div class="highlight-python"><div class="highlight"><pre>import urllib2

2458

import ssl

2459

2460

# This disables all verification

2461

context = ssl._create_unverified_context()

2462

2463

# This allows using a specific certificate for the host, which doesn't need

2464

# to be in the trust store

2465

context = ssl.create_default_context(cafile="/path/to/file.crt")

2466

2467

urllib2.urlopen("https://invalid-cert", context=context)

2468

</pre></div>

2469

</div>

2470

</div>

2471

</div>

2472

2473

<h2>Acknowledgements<a class="headerlink" href="#acknowledgements" title="Permalink to this headline">¶</a></h2>

2474

The author would like to thank the following people for offering

2475

suggestions, corrections and assistance with various drafts of this

2476

article: Nick Coghlan, Philip Jenvey, Ryan Lovett, R. David Murray,

2477

Hugh Secker-Walker.

2478

</div>

2479

</div>

2480

2481

2482

</div>

2483

</div>

2484

</div>

2485

2486

2487

<h3><a href="../contents.html">Table Of Contents</a></h3>

2488

<ul>

2489

<li><a class="reference internal" href="#">What’s New in Python 2.7</a><ul>

2490

<li><a class="reference internal" href="#the-future-for-python-2-x">The Future for Python 2.x</a></li>

2491

<li><a class="reference internal" href="#changes-to-the-handling-of-deprecation-warnings">Changes to the Handling of Deprecation Warnings</a></li>

2492

<li><a class="reference internal" href="#python-3-1-features">Python 3.1 Features</a></li>

2493

<li><a class="reference internal" href="#pep-372-adding-an-ordered-dictionary-to-collections">PEP 372: Adding an Ordered Dictionary to collections</a></li>

2494

<li><a class="reference internal" href="#pep-378-format-specifier-for-thousands-separator">PEP 378: Format Specifier for Thousands Separator</a></li>

2495

<li><a class="reference internal" href="#pep-389-the-argparse-module-for-parsing-command-lines">PEP 389: The argparse Module for Parsing Command Lines</a></li>

2496

<li><a class="reference internal" href="#pep-391-dictionary-based-configuration-for-logging">PEP 391: Dictionary-Based Configuration For Logging</a></li>

2497

<li><a class="reference internal" href="#pep-3106-dictionary-views">PEP 3106: Dictionary Views</a></li>

2498

<li><a class="reference internal" href="#pep-3137-the-memoryview-object">PEP 3137: The memoryview Object</a></li>

2499

<li><a class="reference internal" href="#other-language-changes">Other Language Changes</a><ul>

2500

<li><a class="reference internal" href="#interpreter-changes">Interpreter Changes</a></li>

2501

<li><a class="reference internal" href="#optimizations">Optimizations</a></li>

2502

</ul>

2503

</li>

2504

<li><a class="reference internal" href="#new-and-improved-modules">New and Improved Modules</a><ul>

2505

<li><a class="reference internal" href="#new-module-importlib">New module: importlib</a></li>

2506

<li><a class="reference internal" href="#new-module-sysconfig">New module: sysconfig</a></li>

2507

<li><a class="reference internal" href="#ttk-themed-widgets-for-tk">ttk: Themed Widgets for Tk</a></li>

2508

<li><a class="reference internal" href="#updated-module-unittest">Updated module: unittest</a></li>

2509

<li><a class="reference internal" href="#updated-module-elementtree-1-3">Updated module: ElementTree 1.3</a></li>

2510

</ul>

2511

</li>

2512

<li><a class="reference internal" href="#build-and-c-api-changes">Build and C API Changes</a><ul>

2513

<li><a class="reference internal" href="#capsules">Capsules</a></li>

2514

<li><a class="reference internal" href="#port-specific-changes-windows">Port-Specific Changes: Windows</a></li>

2515

<li><a class="reference internal" href="#port-specific-changes-mac-os-x">Port-Specific Changes: Mac OS X</a></li>

2516

<li><a class="reference internal" href="#port-specific-changes-freebsd">Port-Specific Changes: FreeBSD</a></li>

2517

</ul>

2518

</li>

2519

<li><a class="reference internal" href="#other-changes-and-fixes">Other Changes and Fixes</a></li>

2520

<li><a class="reference internal" href="#porting-to-python-2-7">Porting to Python 2.7</a></li>

2521

<li><a class="reference internal" href="#new-features-added-to-python-2-7-maintenance-releases">New Features Added to Python 2.7 Maintenance Releases</a><ul>

2522

<li><a class="reference internal" href="#pep-434-idle-enhancement-exception-for-all-branches">PEP 434: IDLE Enhancement Exception for All Branches</a></li>

2523

<li><a class="reference internal" href="#pep-466-network-security-enhancements-for-python-2-7">PEP 466: Network Security Enhancements for Python 2.7</a></li>

2524

<li><a class="reference internal" href="#pep-477-backport-ensurepip-pep-453-to-python-2-7">PEP 477: Backport ensurepip (PEP 453) to Python 2.7</a><ul>

2525

<li><a class="reference internal" href="#bootstrapping-pip-by-default">Bootstrapping pip By Default</a></li>

2526

<li><a class="reference internal" href="#documentation-changes">Documentation Changes</a></li>

2527

</ul>

2528

</li>

2529

<li><a class="reference internal" href="#pep-476-enabling-certificate-verification-by-default-for-stdlib-http-clients">PEP 476: Enabling certificate verification by default for stdlib http clients</a></li>

2530

</ul>

2531

</li>

2532

<li><a class="reference internal" href="#acknowledgements">Acknowledgements</a></li>

2533

</ul>

2534

</li>

2535

</ul>

2536

2537

<h4>Previous topic</h4>

2538

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2539

title="previous chapter">What’s New in Python</a>

2540

<h4>Next topic</h4>

2541

<a href="2.6.html"

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title="next chapter">What’s New in Python 2.6</a>

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2545

<li><a href="../bugs.html">Report a Bug</a></li>

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<li><a href="../_sources/whatsnew/2.7.txt"

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rel="nofollow">Show Source</a></li>

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