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<div class="sidemenu"><ul id="lxml-section"><li><span class="section title">lxml</span><ul class="menu foreign" id="index-menu"><li class="menu title"><a href="index.html">lxml</a><ul class="submenu"><li class="menu item"><a href="index.html#introduction">Introduction</a></li><li class="menu item"><a href="index.html#documentation">Documentation</a></li><li class="menu item"><a href="index.html#download">Download</a></li><li class="menu item"><a href="index.html#mailing-list">Mailing list</a></li><li class="menu item"><a href="index.html#bug-tracker">Bug tracker</a></li><li class="menu item"><a href="index.html#license">License</a></li><li class="menu item"><a href="index.html#old-versions">Old Versions</a></li></ul></li></ul><ul class="menu foreign" id="intro-menu"><li class="menu title"><a href="intro.html">Why lxml?</a><ul class="submenu"><li class="menu item"><a href="intro.html#motto">Motto</a></li><li class="menu item"><a href="intro.html#aims">Aims</a></li></ul></li></ul><ul 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interface</a></li><li class="menu item"><a href="parsing.html#iterparse-and-iterwalk">iterparse and iterwalk</a></li><li class="menu item"><a href="parsing.html#python-unicode-strings">Python unicode strings</a></li></ul></li></ul><ul class="menu foreign" id="validation-menu"><li class="menu title"><a href="validation.html">Validation with lxml</a><ul class="submenu"><li class="menu item"><a href="validation.html#validation-at-parse-time">Validation at parse time</a></li><li class="menu item"><a href="validation.html#dtd">DTD</a></li><li class="menu item"><a href="validation.html#relaxng">RelaxNG</a></li><li class="menu item"><a href="validation.html#xmlschema">XMLSchema</a></li><li class="menu item"><a href="validation.html#schematron">Schematron</a></li></ul></li></ul><ul class="menu foreign" id="xpathxslt-menu"><li class="menu title"><a href="xpathxslt.html">XPath and XSLT with lxml</a><ul class="submenu"><li class="menu item"><a href="xpathxslt.html#xpath">XPath</a></li><li 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href="extensions.html#xpath-extension-functions">XPath Extension functions</a></li><li class="menu item"><a href="extensions.html#xslt-extension-elements">XSLT extension elements</a></li></ul></li></ul><ul class="menu foreign" id="element classes-menu"><li class="menu title"><a href="element_classes.html">Using custom Element classes in lxml</a><ul class="submenu"><li class="menu item"><a href="element_classes.html#background-on-element-proxies">Background on Element proxies</a></li><li class="menu item"><a href="element_classes.html#element-initialization">Element initialization</a></li><li class="menu item"><a href="element_classes.html#setting-up-a-class-lookup-scheme">Setting up a class lookup scheme</a></li><li class="menu item"><a href="element_classes.html#generating-xml-with-custom-classes">Generating XML with custom classes</a></li><li class="menu item"><a href="element_classes.html#implementing-namespaces">Implementing namespaces</a></li></ul></li></ul><ul class="menu foreign" id="sax-menu"><li class="menu title"><a href="sax.html">Sax support</a><ul class="submenu"><li class="menu item"><a href="sax.html#building-a-tree-from-sax-events">Building a tree from SAX events</a></li><li class="menu item"><a href="sax.html#producing-sax-events-from-an-elementtree-or-element">Producing SAX events from an ElementTree or Element</a></li><li class="menu item"><a href="sax.html#interfacing-with-pulldom-minidom">Interfacing with pulldom/minidom</a></li></ul></li></ul><ul class="menu foreign" id="capi-menu"><li class="menu title"><a href="capi.html">The public C-API of lxml.etree</a><ul class="submenu"><li class="menu item"><a href="capi.html#writing-external-modules-in-cython">Writing external modules in Cython</a></li><li class="menu item"><a href="capi.html#writing-external-modules-in-c">Writing external modules in C</a></li></ul></li></ul></li></ul><ul id="Developing lxml-section"><li><span class="section title">Developing lxml</span><ul class="menu foreign" id="build-menu"><li class="menu title"><a href="build.html">How to build lxml from source</a><ul class="submenu"><li class="menu item"><a href="build.html#cython">Cython</a></li><li class="menu item"><a href="build.html#subversion">Subversion</a></li><li class="menu item"><a href="build.html#setuptools">Setuptools</a></li><li class="menu item"><a href="build.html#running-the-tests-and-reporting-errors">Running the tests and reporting errors</a></li><li class="menu item"><a href="build.html#building-an-egg">Building an egg</a></li><li class="menu item"><a href="build.html#building-lxml-on-macos-x">Building lxml on MacOS-X</a></li><li class="menu item"><a href="build.html#static-linking-on-windows">Static linking on Windows</a></li><li class="menu item"><a href="build.html#building-debian-packages-from-svn-sources">Building Debian packages from SVN sources</a></li></ul></li></ul><ul class="menu foreign" id="lxml source howto-menu"><li class="menu title"><a href="lxml-source-howto.html">How to read the source of lxml</a><ul class="submenu"><li class="menu item"><a href="lxml-source-howto.html#what-is-cython">What is Cython?</a></li><li class="menu item"><a href="lxml-source-howto.html#where-to-start">Where to start?</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-etree">lxml.etree</a></li><li class="menu item"><a href="lxml-source-howto.html#python-modules">Python modules</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-objectify">lxml.objectify</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-html">lxml.html</a></li></ul></li></ul><ul class="menu foreign" id="changes 2 2 4-menu"><li class="menu title"><a href="changes-2.2.4.html">Release Changelog</a></li></ul><ul class="menu foreign" id="credits-menu"><li class="menu title"><a href="credits.html">Credits</a><ul class="submenu"><li class="menu item"><a href="credits.html#main-contributors">Main contributors</a></li><li class="menu item"><a href="credits.html#special-thanks-goes-to">Special thanks goes to:</a></li></ul></li></ul></li></ul></div><h1 class="title">Parsing XML and HTML with lxml</h1>
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<p>lxml provides a very simple and powerful API for parsing XML and HTML. It
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supports one-step parsing as well as step-by-step parsing using an
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event-driven API (currently only for XML).</p>
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<div class="contents topic">
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<p class="topic-title first"><a id="contents" name="contents">Contents</a></p>
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<div class="contents topic" id="contents">
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<p class="topic-title first">Contents</p>
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<ul class="simple">
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<li><a class="reference" href="#parsers" id="id1" name="id1">Parsers</a><ul>
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<li><a class="reference" href="#parser-options" id="id2" name="id2">Parser options</a></li>
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<li><a class="reference" href="#error-log" id="id3" name="id3">Error log</a></li>
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<li><a class="reference" href="#parsing-html" id="id4" name="id4">Parsing HTML</a></li>
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<li><a class="reference" href="#doctype-information" id="id5" name="id5">Doctype information</a></li>
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<li><a class="reference" href="#the-target-parser-interface" id="id6" name="id6">The target parser interface</a></li>
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<li><a class="reference" href="#the-feed-parser-interface" id="id7" name="id7">The feed parser interface</a></li>
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<li><a class="reference" href="#iterparse-and-iterwalk" id="id8" name="id8">iterparse and iterwalk</a><ul>
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<li><a class="reference" href="#selective-tag-events" id="id9" name="id9">Selective tag events</a></li>
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<li><a class="reference" href="#comments-and-pis" id="id10" name="id10">Comments and PIs</a></li>
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<li><a class="reference" href="#modifying-the-tree" id="id11" name="id11">Modifying the tree</a></li>
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<li><a class="reference" href="#iterwalk" id="id12" name="id12">iterwalk</a></li>
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<li><a class="reference" href="#python-unicode-strings" id="id13" name="id13">Python unicode strings</a><ul>
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<li><a class="reference" href="#serialising-to-unicode-strings" id="id14" name="id14">Serialising to Unicode strings</a></li>
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<li><a class="reference internal" href="#parsers" id="id1">Parsers</a><ul>
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<li><a class="reference internal" href="#parser-options" id="id2">Parser options</a></li>
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<li><a class="reference internal" href="#error-log" id="id3">Error log</a></li>
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<li><a class="reference internal" href="#parsing-html" id="id4">Parsing HTML</a></li>
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<li><a class="reference internal" href="#doctype-information" id="id5">Doctype information</a></li>
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<li><a class="reference internal" href="#the-target-parser-interface" id="id6">The target parser interface</a></li>
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<li><a class="reference internal" href="#the-feed-parser-interface" id="id7">The feed parser interface</a></li>
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<li><a class="reference internal" href="#iterparse-and-iterwalk" id="id8">iterparse and iterwalk</a><ul>
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<li><a class="reference internal" href="#selective-tag-events" id="id9">Selective tag events</a></li>
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<li><a class="reference internal" href="#comments-and-pis" id="id10">Comments and PIs</a></li>
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<li><a class="reference internal" href="#modifying-the-tree" id="id11">Modifying the tree</a></li>
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<li><a class="reference internal" href="#iterwalk" id="id12">iterwalk</a></li>
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<li><a class="reference internal" href="#python-unicode-strings" id="id13">Python unicode strings</a><ul>
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<li><a class="reference internal" href="#serialising-to-unicode-strings" id="id14">Serialising to Unicode strings</a></li>
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<p>The usual setup procedure:</p>
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<div class="syntax"><pre><span class="gp">>>> </span><span class="k">from</span> <span class="nn">lxml</span> <span class="k">import</span> <span class="n">etree</span>
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<div class="syntax"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">lxml</span> <span class="kn">import</span> <span class="n">etree</span>
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<h1><a id="parsers" name="parsers">Parsers</a></h1>
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<div class="section" id="parsers">
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<p>Parsers are represented by parser objects. There is support for parsing both
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XML and (broken) HTML. Note that XHTML is best parsed as XML, parsing it with
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the HTML parser can lead to unexpected results. Here is a simple example for
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the default attributes from it</li>
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<li>dtd_validation - validate while parsing (if a DTD was referenced)</li>
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<li>load_dtd - load and parse the DTD while parsing (no validation is performed)</li>
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<li>no_network - prevent network access when looking up external documents</li>
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<li>no_network - prevent network access when looking up external
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documents (on by default)</li>
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<li>ns_clean - try to clean up redundant namespace declarations</li>
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<li>recover - try hard to parse through broken XML</li>
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<li>remove_blank_text - discard blank text nodes between tags</li>
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<li>remove_comments - discard comments</li>
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<li>remove_pis - discard processing instructions</li>
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<li>strip_cdata - replace CDATA sections by normal text content (on by
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<li>resolve_entities - replace entities by their text value (on by
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<li>huge_tree - disable security restrictions and support very deep trees
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and very long text content (only affects libxml2 2.7+)</li>
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<li>compact - use compact storage for short text content (on by default)</li>
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<h2><a id="error-log" name="error-log">Error log</a></h2>
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<div class="section" id="error-log">
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<p>Parsers have an <tt class="docutils literal"><span class="pre">error_log</span></tt> property that lists the errors of the
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last parser run:</p>
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<div class="syntax"><pre><span class="gp">>>> </span><span class="n">parser</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XMLParser</span><span class="p">()</span>
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<span class="gp">>>> </span><span class="n">tree</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="s">"<root></b>"</span><span class="p">,</span> <span class="n">parser</span><span class="p">)</span>
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<span class="gt">Traceback (most recent call last):</span>
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<span class="c">...</span>
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<span class="c">...</span>
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<span class="nc">lxml.etree.XMLSyntaxError: Opening and ending tag mismatch</span>: <span class="n-Identifier">root line 1 and b, line 1, column 11</span>
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<span class="gp">>>> </span><span class="k">print</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">parser</span><span class="o">.</span><span class="n">error_log</span><span class="p">))</span>
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<span class="go">1</span>
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<span class="gp">>>> </span><span class="n">error</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">error_log</span><span class="p">[</span><span class="mf">0</span><span class="p">]</span>
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<span class="gp">>>> </span><span class="n">error</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">error_log</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
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<span class="gp">>>> </span><span class="k">print</span><span class="p">(</span><span class="n">error</span><span class="o">.</span><span class="n">message</span><span class="p">)</span>
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<span class="go">Opening and ending tag mismatch: root line 1 and b</span>
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<span class="gp">>>> </span><span class="k">print</span><span class="p">(</span><span class="n">error</span><span class="o">.</span><span class="n">line</span><span class="p">)</span>
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<span class="go">11</span>
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<div class="section">
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<h2><a id="parsing-html" name="parsing-html">Parsing HTML</a></h2>
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<p>HTML parsing is similarly simple. The parsers have a <tt class="docutils literal"><span class="pre">recover</span></tt> keyword
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argument that the HTMLParser sets by default. It lets libxml2 try its best to
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return something usable without raising an exception. You should use libxml2
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version 2.6.21 or newer to take advantage of this feature:</p>
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<div class="section" id="parsing-html">
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<h2>Parsing HTML</h2>
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<p>HTML parsing is similarly simple. The parsers have a <tt class="docutils literal"><span class="pre">recover</span></tt>
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keyword argument that the HTMLParser sets by default. It lets libxml2
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try its best to return a valid HTML tree with all content it can
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manage to parse. It will not raise an exception on parser errors.
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You should use libxml2 version 2.6.21 or newer to take advantage of
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<div class="syntax"><pre><span class="gp">>>> </span><span class="n">broken_html</span> <span class="o">=</span> <span class="s">"<html><head><title>test<body><h1>page title</h3>"</span>
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<span class="gp">>>> </span><span class="n">parser</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">HTMLParser</span><span class="p">()</span>
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parser may have to drop seriously broken parts when struggling to keep
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parsing. Especially misplaced meta tags can suffer from this, which may lead
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to encoding problems.</p>
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<p>Note that the result is a valid HTML tree, but it may not be a
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well-formed XML tree. For example, XML forbids double hyphens in
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comments, which the HTML parser will happily accept in recovery mode.
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Therefore, if your goal is to serialise an HTML document as an
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XML/XHTML document after parsing, you may have to apply some manual
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preprocessing first.</p>
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<div class="section">
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<h2><a id="doctype-information" name="doctype-information">Doctype information</a></h2>
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<div class="section" id="doctype-information">
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<h2>Doctype information</h2>
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<p>The use of the libxml2 parsers makes some additional information available at
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the API level. Currently, ElementTree objects can access the DOCTYPE
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information provided by a parsed document, as well as the XML version and the
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<div class="section">
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<h1><a id="the-target-parser-interface" name="the-target-parser-interface">The target parser interface</a></h1>
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<p><a class="reference" href="http://effbot.org/elementtree/elementtree-xmlparser.htm">As in ElementTree</a>, and similar to a SAX event handler, you can pass
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<div class="section" id="the-target-parser-interface">
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<h1>The target parser interface</h1>
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<p><a class="reference external" href="http://effbot.org/elementtree/elementtree-xmlparser.htm">As in ElementTree</a>, and similar to a SAX event handler, you can pass
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a target object to the parser:</p>
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<div class="syntax"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">EchoTarget</span><span class="p">:</span>
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<span class="gp">... </span> <span class="k">def</span> <span class="nf">start</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">tag</span><span class="p">,</span> <span class="n">attrib</span><span class="p">):</span>
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<span class="gp">>>> </span><span class="n">parser</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XMLParser</span><span class="p">(</span><span class="n">target</span> <span class="o">=</span> <span class="n">EchoTarget</span><span class="p">())</span>
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<span class="gp">>>> </span><span class="n">result</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="s">"<element>some<!--comment-->text</element>"</span><span class="p">,</span> <span class="n">parser</span><span class="p">)</span>
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<span class="go">start element {}</span>
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<span class="go">data u'some'</span>
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<span class="go">comment comment</span>
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<span class="go">data u'text'</span>
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<span class="go">end element</span>
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<span class="go">close</span>
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<span class="gp">>>> </span><span class="k">print</span><span class="p">(</span><span class="n">result</span><span class="p">)</span>
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<span class="go">closed!</span>
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<p>Note that the parser does <em>not</em> build a tree in this case. The result
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of the parser run is whatever the target object returns from its
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<tt class="docutils literal"><span class="pre">close()</span></tt> method. If you want to return an XML tree here, you have
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to create it programmatically in the target object. An example for a
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parser target that builds a tree is the <tt class="docutils literal"><span class="pre">TreeBuilder</span></tt>.</p>
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<span class="gp">>>> </span><span class="n">result</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="s">"<element>some<!--comment-->text</element>"</span><span class="p">,</span>
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<span class="gp">... </span> <span class="n">parser</span><span class="p">)</span>
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<span class="go">start element {}</span>
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<span class="go">data u'some'</span>
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<span class="go">comment comment</span>
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<span class="go">data u'text'</span>
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<span class="go">end element</span>
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<span class="go">close</span>
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<span class="gp">>>> </span><span class="k">print</span><span class="p">(</span><span class="n">result</span><span class="p">)</span>
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<span class="go">closed!</span>
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<p>It is important for the <tt class="docutils literal"><span class="pre">.close()</span></tt> method to reset the parser target
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to a usable state, so that you can reuse the parser as often as you
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<div class="syntax"><pre><span class="gp">>>> </span><span class="n">result</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="s">"<element>some<!--comment-->text</element>"</span><span class="p">,</span>
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<span class="gp">... </span> <span class="n">parser</span><span class="p">)</span>
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<span class="go">start element {}</span>
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<span class="go">data u'some'</span>
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<span class="go">comment comment</span>
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<span class="go">data u'text'</span>
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<span class="go">end element</span>
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<span class="go">close</span>
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<span class="gp">>>> </span><span class="k">print</span><span class="p">(</span><span class="n">result</span><span class="p">)</span>
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<span class="go">closed!</span>
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<p>Note that the parser does <em>not</em> build a tree when using a parser
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target. The result of the parser run is whatever the target object
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returns from its <tt class="docutils literal"><span class="pre">.close()</span></tt> method. If you want to return an XML
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tree here, you have to create it programmatically in the target
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object. An example for a parser target that builds a tree is the
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<tt class="docutils literal"><span class="pre">TreeBuilder</span></tt>.</p>
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<pre class="doctest-block">
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>>> parser = etree.XMLParser(target = etree.TreeBuilder())
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<pre class="doctest-block">
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>>> result = etree.XML("<element>some<!--comment-->text</element>", parser)
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>>> result = etree.XML("<element>some<!--comment-->text</element>",
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<pre class="doctest-block">
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>>> print(result.tag)
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<div class="section">
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<h1><a id="the-feed-parser-interface" name="the-feed-parser-interface">The feed parser interface</a></h1>
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<div class="section" id="the-feed-parser-interface">
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<h1>The feed parser interface</h1>
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<p>Since lxml 2.0, the parsers have a feed parser interface that is
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compatible to the <a class="reference" href="http://effbot.org/elementtree/elementtree-xmlparser.htm">ElementTree parsers</a>. You can use it to feed data
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compatible to the <a class="reference external" href="http://effbot.org/elementtree/elementtree-xmlparser.htm">ElementTree parsers</a>. You can use it to feed data
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into the parser in a controlled step-by-step way.</p>
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<p>In lxml.etree, you can use both interfaces to a parser at the same
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time: the <tt class="docutils literal"><span class="pre">parse()</span></tt> or <tt class="docutils literal"><span class="pre">XML()</span></tt> functions, and the feed parser
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corresponding <tt class="docutils literal"><span class="pre">end-ns</span></tt> event does not have a value (None). It is
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common practice to use a list as namespace stack and pop the last
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entry on the 'end-ns' event.</p>
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<div class="syntax"><pre><span class="gp">>>> </span><span class="k">print</span><span class="p">(</span><span class="n">xml</span><span class="p">[:</span><span class="o">-</span><span class="mf">1</span><span class="p">])</span>
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<div class="syntax"><pre><span class="gp">>>> </span><span class="k">print</span><span class="p">(</span><span class="n">xml</span><span class="p">[:</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span>
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<span class="go"><root></span>
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<span class="go"> <element key='value'>text</element></span>
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<span class="go"> <element>text</element>tail</span>
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<span class="gp">... </span> <span class="c"># ... do something with the element</span>
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<span class="gp">... </span> <span class="n">element</span><span class="o">.</span><span class="n">clear</span><span class="p">()</span> <span class="c"># clean up children</span>
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<span class="gp">... </span> <span class="k">while</span> <span class="n">element</span><span class="o">.</span><span class="n">getprevious</span><span class="p">()</span> <span class="ow">is</span> <span class="ow">not</span> <span class="bp">None</span><span class="p">:</span>
475
<span class="gp">... </span> <span class="k">del</span> <span class="n">element</span><span class="o">.</span><span class="n">getparent</span><span class="p">()[</span><span class="mf">0</span><span class="p">]</span> <span class="c"># clean up preceding siblings</span>
510
<span class="gp">... </span> <span class="k">del</span> <span class="n">element</span><span class="o">.</span><span class="n">getparent</span><span class="p">()[</span><span class="mi">0</span><span class="p">]</span> <span class="c"># clean up preceding siblings</span>
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512
<p>The <tt class="docutils literal"><span class="pre">while</span></tt> loop deletes multiple siblings in a row. This is only necessary
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if you skipped over some of them using the <tt class="docutils literal"><span class="pre">tag</span></tt> keyword argument.
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encoding themselves and thus lie about their real encoding:</p>
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<div class="syntax"><pre><span class="gp">>>> </span><span class="n">etree</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span> <span class="s">u'<?xml version="1.0" encoding="ASCII"?></span><span class="se">\n</span><span class="s">'</span> <span class="o">+</span> <span class="n">uxml</span> <span class="p">)</span>
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<span class="gt">Traceback (most recent call last):</span>
528
<span class="c">...</span>
563
<span class="c">...</span>
529
564
<span class="nc">ValueError</span>: <span class="n-Identifier">Unicode strings with encoding declaration are not supported.</span>
531
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<p>Similarly, you will get errors when you try the same with HTML data in a
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unicode string that specifies a charset in a meta tag of the header. You
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568
should generally avoid converting XML/HTML data to unicode before passing it
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569
into the parsers. It is both slower and error prone.</p>
535
<div class="section">
536
<h2><a id="serialising-to-unicode-strings" name="serialising-to-unicode-strings">Serialising to Unicode strings</a></h2>
570
<div class="section" id="serialising-to-unicode-strings">
571
<h2>Serialising to Unicode strings</h2>
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<p>To serialize the result, you would normally use the <tt class="docutils literal"><span class="pre">tostring()</span></tt>
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module function, which serializes to plain ASCII by default or a
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number of other byte encodings if asked for:</p>
added
removed
doc/html/parsing.html
