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<div class="section" id="types">
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<span id="id1"></span><h1>Types<a class="headerlink" href="#types" title="Permalink to this headline">¶</a></h1>
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<p>Read about <a class="reference external" href="http://www.sqlite.org/datatype3.html">SQLite 3 types</a>. ASPW always maintains the
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correct type for values, and never converts them to something
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else. Note however that SQLite may convert types based on column
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affinity as <a class="reference external" href="http://www.sqlite.org/datatype3.html">described</a>. ASPW
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requires that all values supplied are one of the corresponding
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Python/SQLite types (or a subclass).</p>
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<div class="section" id="mapping">
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<h2>Mapping<a class="headerlink" href="#mapping" title="Permalink to this headline">¶</a></h2>
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<li>None in Python is NULL in SQLite</li>
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<li>Python int or long is INTEGER in SQLite. The value represented must
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fit within a 64 bit signed quantity (long long at the C level) or an
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overflow exception is generated.</li>
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<li>Python’s float type is used for REAL in SQLite. (At the C level they
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are both 8 byte quantities and there is no loss of precision).</li>
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<li>In Python 2, Python’s string or unicode is used for TEXT supplied to
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SQLite and all text returned from SQLite is unicode. For Python 3
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only unicode is used.</li>
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<li>For Python 2 the buffer class is used for BLOB in SQLite. In Python
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3 the bytes type is used, although you can still supply buffers.</li>
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<div class="section" id="unicode">
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<span id="id2"></span><h2>Unicode<a class="headerlink" href="#unicode" title="Permalink to this headline">¶</a></h2>
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<p>All SQLite strings are Unicode. The actual binary representations can
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be UTF8, or UTF16 in either byte order. ASPW uses the UTF8 interface
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to SQLite which results in the binary string representation in your
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database defaulting to UTF8 as well. All this is totally transparent
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to your Python code.</p>
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<p>Everywhere strings are used (eg as database values, SQL statements,
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bindings names, user defined functions) you can use Unicode strings,
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and in Python 3 must use Unicode. In Python 2, you can also use the
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bare Python string class, and ASPW will automatically call the unicode
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converter if any non-ascii characters are present.</p>
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<p>When returning text values from SQLite, ASPW always uses the Python
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<p>If you don’t know much about Unicode then read <a class="reference external" href="http://www.joelonsoftware.com/articles/Unicode.html">Joel’s article</a>. SQLite does
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not include conversion from random non-Unicode encodings to or from
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Unicode. (It does include conversion between 8 bit and 16 bit Unicode
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encodings). Python includes <a class="reference external" href="http://www.python.org/doc/2.5.2/lib/module-codecs.html">codecs</a> for
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conversion to or from many different character sets.</p>
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<p>If you don’t want to use Unicode and instead want a simple bytes in
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are the same bytes out then you should only use blobs.</p>
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<p>If you want to do manipulation of unicode text such as upper/lower
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casing or sorting then you need to know about locales. This is
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because the exact same sequence of characters sort, upper case, lower
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case etc differently depending on where you are. As an example Turkic
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languages have multiple letter i, German has ß which behaves like ss,
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various accents sort differently in different European countries.
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Fortunately there is a libary you can ask to do the right locale
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specific thing <a class="reference external" href="http://en.wikipedia.org/wiki/International_Components_for_Unicode">ICU</a>.
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A default SQLite compilation only deals with the 26 letter Roman
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alphabet. If you enable ICU with SQLite then you get <a class="reference external" href="http://www.sqlite.org/src/finfo?name=ext/icu/README.txt">good stuff</a>.
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See the <a class="reference external" href="build.html#building"><em>Building</em></a> section on how to enable ICU for SQLite with
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APSW. Note that Python does not currently include ICU support and
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hence sorting, upper/lower casing etc are limited and do not take
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locales into account.</p>
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<p>In summary, never confuse bytes with strings (which C sadly treats as
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the same thing). Either always use bytes (and SQLite blobs) for
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everything or use strings (and SQLite strings) for everything. If you
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take the latter approach and have to deal with external input/output
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then you must know what encodings are being used and it is best to
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convert to Unicode as early as possible on input and late as possible on
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<h3><a href="index.html">Table Of Contents</a></h3>
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<li><a class="reference external" href="#">Types</a><ul>
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<li><a class="reference external" href="#mapping">Mapping</a></li>
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<li><a class="reference external" href="#unicode">Unicode</a></li>
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<h4>Previous topic</h4>
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title="previous chapter">Exceptions</a></p>
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© <a href="copyright.html">Copyright</a> 2004-2009, Roger Binns <rogerb@rogerbinns.com>.
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