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   6 <title>The lxml.etree Tutorial</title>
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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#support-the-project">Support the project</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><li class="menu item"><a href="index.html#legal-notice-for-donations">Legal Notice for Donations</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 class="menu foreign" id="installation-menu"><li class="menu title"><a href="installation.html">Installing lxml</a><ul class="submenu"><li class="menu item"><a href="installation.html#requirements">Requirements</a></li><li class="menu item"><a href="installation.html#installation">Installation</a></li><li class="menu item"><a href="installation.html#building-lxml-from-sources">Building lxml from sources</a></li><li class="menu item"><a href="installation.html#using-lxml-with-python-libxml2">Using lxml with python-libxml2</a></li><li class="menu item"><a href="installation.html#ms-windows">MS Windows</a></li><li class="menu item"><a href="installation.html#macos-x">MacOS-X</a></li></ul></li></ul><ul class="menu foreign" id="performance-menu"><li class="menu title"><a href="performance.html">Benchmarks and Speed</a><ul class="submenu"><li class="menu item"><a href="performance.html#general-notes">General notes</a></li><li class="menu item"><a href="performance.html#how-to-read-the-timings">How to read the timings</a></li><li class="menu item"><a href="performance.html#parsing-and-serialising">Parsing and Serialising</a></li><li class="menu item"><a href="performance.html#the-elementtree-api">The ElementTree API</a></li><li class="menu item"><a href="performance.html#xpath">XPath</a></li><li class="menu item"><a href="performance.html#a-longer-example">A longer example</a></li><li class="menu item"><a href="performance.html#lxml-objectify">lxml.objectify</a></li></ul></li></ul><ul class="menu foreign" id="compatibility-menu"><li class="menu title"><a href="compatibility.html">ElementTree compatibility of lxml.etree</a></li></ul><ul class="menu foreign" id="FAQ-menu"><li class="menu title"><a href="FAQ.html">lxml FAQ - Frequently Asked Questions</a><ul class="submenu"><li class="menu item"><a href="FAQ.html#general-questions">General Questions</a></li><li class="menu item"><a href="FAQ.html#installation">Installation</a></li><li class="menu item"><a href="FAQ.html#contributing">Contributing</a></li><li class="menu item"><a href="FAQ.html#bugs">Bugs</a></li><li class="menu item"><a href="FAQ.html#id1">Threading</a></li><li class="menu item"><a href="FAQ.html#parsing-and-serialisation">Parsing and Serialisation</a></li><li class="menu item"><a href="FAQ.html#xpath-and-document-traversal">XPath and Document Traversal</a></li></ul></li></ul></li></ul><ul id="Developing with lxml-section"><li><span class="section title">Developing with lxml</span><ul class="menu current" id="tutorial-menu"><li class="menu title"><a href="tutorial.html">The lxml.etree Tutorial</a><ul class="submenu"><li class="menu item"><a href="tutorial.html#the-element-class">The Element class</a></li><li class="menu item"><a href="tutorial.html#the-elementtree-class">The ElementTree class</a></li><li class="menu item"><a href="tutorial.html#parsing-from-strings-and-files">Parsing from strings and files</a></li><li class="menu item"><a href="tutorial.html#namespaces">Namespaces</a></li><li class="menu item"><a href="tutorial.html#the-e-factory">The E-factory</a></li><li class="menu item"><a href="tutorial.html#elementpath">ElementPath</a></li></ul></li></ul><ul class="menu foreign" id="api index-menu"><li class="menu title"><a href="api/index.html">API reference</a></li></ul><ul class="menu foreign" id="api-menu"><li class="menu title"><a href="api.html">APIs specific to lxml.etree</a><ul class="submenu"><li class="menu item"><a href="api.html#lxml-etree">lxml.etree</a></li><li class="menu item"><a href="api.html#other-element-apis">Other Element APIs</a></li><li class="menu item"><a href="api.html#trees-and-documents">Trees and Documents</a></li><li class="menu item"><a href="api.html#iteration">Iteration</a></li><li class="menu item"><a href="api.html#error-handling-on-excepti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 to:</a></li></ul></li></ul></li><li><a href="http://lxml.de/sitemap.html">Sitemap</a></li></ul></div><h1 class="title">The lxml.etree Tutorial</h1>
  15 <table class="docinfo" frame="void" rules="none">
  16 <col class="docinfo-name" />
  17 <col class="docinfo-content" />
  18 <tbody valign="top">
  19 <tr><th class="docinfo-name">Author:</th>
  20 <td>Stefan Behnel</td></tr>
  21 </tbody>
  22 </table>
  23 <p>This is a tutorial on XML processing with <tt class="docutils literal">lxml.etree</tt>.  It briefly
  24 overviews the main concepts of the <a class="reference external" href="http://effbot.org/zone/element-index.htm#documentation">ElementTree API</a>, and some simple
  25 enhancements that make your life as a programmer easier.</p>
  26 <p>For a complete reference of the API, see the <a class="reference external" href="api/index.html">generated API
  27 documentation</a>.</p>
  28 <div class="contents topic" id="contents">
  29 <p class="topic-title first">Contents</p>
  30 <ul class="simple">
  31 <li><a class="reference internal" href="#the-element-class" id="id2">The Element class</a><ul>
  32 <li><a class="reference internal" href="#elements-are-lists" id="id3">Elements are lists</a></li>
  33 <li><a class="reference internal" href="#elements-carry-attributes" id="id4">Elements carry attributes</a></li>
  34 <li><a class="reference internal" href="#elements-contain-text" id="id5">Elements contain text</a></li>
  35 <li><a class="reference internal" href="#using-xpath-to-find-text" id="id6">Using XPath to find text</a></li>
  36 <li><a class="reference internal" href="#tree-iteration" id="id7">Tree iteration</a></li>
  37 <li><a class="reference internal" href="#serialisation" id="id8">Serialisation</a></li>
  38 </ul>
  39 </li>
  40 <li><a class="reference internal" href="#the-elementtree-class" id="id9">The ElementTree class</a></li>
  41 <li><a class="reference internal" href="#parsing-from-strings-and-files" id="id10">Parsing from strings and files</a><ul>
  42 <li><a class="reference internal" href="#the-fromstring-function" id="id11">The fromstring() function</a></li>
  43 <li><a class="reference internal" href="#the-xml-function" id="id12">The XML() function</a></li>
  44 <li><a class="reference internal" href="#the-parse-function" id="id13">The parse() function</a></li>
  45 <li><a class="reference internal" href="#parser-objects" id="id14">Parser objects</a></li>
  46 <li><a class="reference internal" href="#incremental-parsing" id="id15">Incremental parsing</a></li>
  47 <li><a class="reference internal" href="#event-driven-parsing" id="id16">Event-driven parsing</a></li>
  48 </ul>
  49 </li>
  50 <li><a class="reference internal" href="#namespaces" id="id17">Namespaces</a></li>
  51 <li><a class="reference internal" href="#the-e-factory" id="id18">The E-factory</a></li>
  52 <li><a class="reference internal" href="#elementpath" id="id19">ElementPath</a></li>
  53 </ul>
  54 </div>
  55 <p>A common way to import <tt class="docutils literal">lxml.etree</tt> is as follows:</p>
  56 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">lxml</span> <span class="kn">import</span> <span class="n">etree</span>
  57 </pre></div>
  58 <p>If your code only uses the ElementTree API and does not rely on any
  59 functionality that is specific to <tt class="docutils literal">lxml.etree</tt>, you can also use (any part
  60 of) the following import chain as a fall-back to the original ElementTree:</p>
  61 <div class="syntax"><pre><span class="k">try</span><span class="p">:</span>
  62   <span class="kn">from</span> <span class="nn">lxml</span> <span class="kn">import</span> <span class="n">etree</span>
  63   <span class="k">print</span><span class="p">(</span><span class="s">"running with lxml.etree"</span><span class="p">)</span>
  64 <span class="k">except</span> <span class="ne">ImportError</span><span class="p">:</span>
  65   <span class="k">try</span><span class="p">:</span>
  66     <span class="c"># Python 2.5</span>
  67     <span class="kn">import</span> <span class="nn">xml.etree.cElementTree</span> <span class="kn">as</span> <span class="nn">etree</span>
  68     <span class="k">print</span><span class="p">(</span><span class="s">"running with cElementTree on Python 2.5+"</span><span class="p">)</span>
  69   <span class="k">except</span> <span class="ne">ImportError</span><span class="p">:</span>
  70     <span class="k">try</span><span class="p">:</span>
  71       <span class="c"># Python 2.5</span>
  72       <span class="kn">import</span> <span class="nn">xml.etree.ElementTree</span> <span class="kn">as</span> <span class="nn">etree</span>
  73       <span class="k">print</span><span class="p">(</span><span class="s">"running with ElementTree on Python 2.5+"</span><span class="p">)</span>
  74     <span class="k">except</span> <span class="ne">ImportError</span><span class="p">:</span>
  75       <span class="k">try</span><span class="p">:</span>
  76         <span class="c"># normal cElementTree install</span>
  77         <span class="kn">import</span> <span class="nn">cElementTree</span> <span class="kn">as</span> <span class="nn">etree</span>
  78         <span class="k">print</span><span class="p">(</span><span class="s">"running with cElementTree"</span><span class="p">)</span>
  79       <span class="k">except</span> <span class="ne">ImportError</span><span class="p">:</span>
  80         <span class="k">try</span><span class="p">:</span>
  81           <span class="c"># normal ElementTree install</span>
  82           <span class="kn">import</span> <span class="nn">elementtree.ElementTree</span> <span class="kn">as</span> <span class="nn">etree</span>
  83           <span class="k">print</span><span class="p">(</span><span class="s">"running with ElementTree"</span><span class="p">)</span>
  84         <span class="k">except</span> <span class="ne">ImportError</span><span class="p">:</span>
  85           <span class="k">print</span><span class="p">(</span><span class="s">"Failed to import ElementTree from any known place"</span><span class="p">)</span>
  86 </pre></div>
  87 <p>To aid in writing portable code, this tutorial makes it clear in the examples
  88 which part of the presented API is an extension of lxml.etree over the
  89 original <a class="reference external" href="http://effbot.org/zone/element-index.htm#documentation">ElementTree API</a>, as defined by Fredrik Lundh's <a class="reference external" href="http://effbot.org/zone/element-index.htm">ElementTree
  90 library</a>.</p>
  91 <div class="section" id="the-element-class">
  92 <h1>The Element class</h1>
  93 <p>An <tt class="docutils literal">Element</tt> is the main container object for the ElementTree API.  Most of
  94 the XML tree functionality is accessed through this class.  Elements are
  95 easily created through the <tt class="docutils literal">Element</tt> factory:</p>
  96 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"root"</span><span class="p">)</span>
  97 </pre></div>
  98 <p>The XML tag name of elements is accessed through the <tt class="docutils literal">tag</tt> property:</p>
  99 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 100 <span class="go">root</span>
 101 </pre></div>
 102 <p>Elements are organised in an XML tree structure.  To create child elements and
 103 add them to a parent element, you can use the <tt class="docutils literal">append()</tt> method:</p>
 104 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="o">.</span><span class="n">append</span><span class="p">(</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"child1"</span><span class="p">)</span> <span class="p">)</span>
 105 </pre></div>
 106 <p>However, this is so common that there is a shorter and much more efficient way
 107 to do this: the <tt class="docutils literal">SubElement</tt> factory.  It accepts the same arguments as the
 108 <tt class="docutils literal">Element</tt> factory, but additionally requires the parent as first argument:</p>
 109 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">child2</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s">"child2"</span><span class="p">)</span>
 110 <span class="gp">&gt;&gt;&gt; </span><span class="n">child3</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s">"child3"</span><span class="p">)</span>
 111 </pre></div>
 112 <p>To see that this is really XML, you can serialise the tree you have created:</p>
 113 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 114 <span class="go">&lt;root&gt;</span>
 115 <span class="go">  &lt;child1/&gt;</span>
 116 <span class="go">  &lt;child2/&gt;</span>
 117 <span class="go">  &lt;child3/&gt;</span>
 118 <span class="go">&lt;/root&gt;</span>
 119 </pre></div>
 120 <div class="section" id="elements-are-lists">
 121 <h2>Elements are lists</h2>
 122 <p>To make the access to these subelements as easy and straight forward as
 123 possible, elements behave like normal Python lists:</p>
 124 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">child</span> <span class="o">=</span> <span class="n">root</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
 125 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">child</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 126 <span class="go">child1</span>
 127
 128 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">root</span><span class="p">))</span>
 129 <span class="go">3</span>
 130
 131 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="o">.</span><span class="n">index</span><span class="p">(</span><span class="n">root</span><span class="p">[</span><span class="mi">1</span><span class="p">])</span> <span class="c"># lxml.etree only!</span>
 132 <span class="go">1</span>
 133
 134 <span class="gp">&gt;&gt;&gt; </span><span class="n">children</span> <span class="o">=</span> <span class="nb">list</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 135
 136 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">child</span> <span class="ow">in</span> <span class="n">root</span><span class="p">:</span>
 137 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="n">child</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 138 <span class="go">child1</span>
 139 <span class="go">child2</span>
 140 <span class="go">child3</span>
 141
 142 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="o">.</span><span class="n">insert</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"child0"</span><span class="p">))</span>
 143 <span class="gp">&gt;&gt;&gt; </span><span class="n">start</span> <span class="o">=</span> <span class="n">root</span><span class="p">[:</span><span class="mi">1</span><span class="p">]</span>
 144 <span class="gp">&gt;&gt;&gt; </span><span class="n">end</span>   <span class="o">=</span> <span class="n">root</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">:]</span>
 145
 146 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">start</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 147 <span class="go">child0</span>
 148 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">end</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 149 <span class="go">child3</span>
 150
 151 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="n">root</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="c"># this moves the element in lxml.etree!</span>
 152 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">child</span> <span class="ow">in</span> <span class="n">root</span><span class="p">:</span>
 153 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="n">child</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 154 <span class="go">child3</span>
 155 <span class="go">child1</span>
 156 <span class="go">child2</span>
 157 </pre></div>
 158 <p>Prior to ElementTree 1.3 and lxml 2.0, you could also check the truth value of
 159 an Element to see if it has children, i.e. if the list of children is empty.
 160 This is no longer supported as people tend to find it surprising that a
 161 non-None reference to an existing Element can evaluate to False.  Instead, use
 162 <tt class="docutils literal">len(element)</tt>, which is both more explicit and less error prone.</p>
 163 <p>Note in the examples that the last element was <em>moved</em> to a different position
 164 in the last example.  This is a difference from the original ElementTree (and
 165 from lists), where elements can sit in multiple positions of any number of
 166 trees.  In lxml.etree, elements can only sit in one position of one tree at a
 167 time.</p>
 168 <p>If you want to <em>copy</em> an element to a different position, consider creating an
 169 independent <em>deep copy</em> using the <tt class="docutils literal">copy</tt> module from Python's standard
 170 library:</p>
 171 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">copy</span> <span class="kn">import</span> <span class="n">deepcopy</span>
 172
 173 <span class="gp">&gt;&gt;&gt; </span><span class="n">element</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"neu"</span><span class="p">)</span>
 174 <span class="gp">&gt;&gt;&gt; </span><span class="n">element</span><span class="o">.</span><span class="n">append</span><span class="p">(</span> <span class="n">deepcopy</span><span class="p">(</span><span class="n">root</span><span class="p">[</span><span class="mi">1</span><span class="p">])</span> <span class="p">)</span>
 175
 176 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">element</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 177 <span class="go">child1</span>
 178 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">([</span> <span class="n">c</span><span class="o">.</span><span class="n">tag</span> <span class="k">for</span> <span class="n">c</span> <span class="ow">in</span> <span class="n">root</span> <span class="p">])</span>
 179 <span class="go">['child3', 'child1', 'child2']</span>
 180 </pre></div>
 181 <p>The way up in the tree is provided through the <tt class="docutils literal">getparent()</tt> method:</p>
 182 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="ow">is</span> <span class="n">root</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">getparent</span><span class="p">()</span>  <span class="c"># lxml.etree only!</span>
 183 <span class="go">True</span>
 184 </pre></div>
 185 <p>The siblings (or neighbours) of an element are accessed as next and previous
 186 elements:</p>
 187 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="ow">is</span> <span class="n">root</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">getprevious</span><span class="p">()</span> <span class="c"># lxml.etree only!</span>
 188 <span class="go">True</span>
 189 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="ow">is</span> <span class="n">root</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">getnext</span><span class="p">()</span> <span class="c"># lxml.etree only!</span>
 190 <span class="go">True</span>
 191 </pre></div>
 192 </div>
 193 <div class="section" id="elements-carry-attributes">
 194 <h2>Elements carry attributes</h2>
 195 <p>XML elements support attributes.  You can create them directly in the Element
 196 factory:</p>
 197 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"root"</span><span class="p">,</span> <span class="n">interesting</span><span class="o">=</span><span class="s">"totally"</span><span class="p">)</span>
 198 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 199 <span class="go">b'&lt;root interesting="totally"/&gt;'</span>
 200 </pre></div>
 201 <p>Fast and direct access to these attributes is provided by the <tt class="docutils literal">set()</tt> and
 202 <tt class="docutils literal">get()</tt> methods of elements:</p>
 203 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">"interesting"</span><span class="p">))</span>
 204 <span class="go">totally</span>
 205
 206 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="s">"interesting"</span><span class="p">,</span> <span class="s">"somewhat"</span><span class="p">)</span>
 207 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">"interesting"</span><span class="p">))</span>
 208 <span class="go">somewhat</span>
 209 </pre></div>
 210 <p>However, a very convenient way of dealing with them is through the dictionary
 211 interface of the <tt class="docutils literal">attrib</tt> property:</p>
 212 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">attributes</span> <span class="o">=</span> <span class="n">root</span><span class="o">.</span><span class="n">attrib</span>
 213
 214 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">attributes</span><span class="p">[</span><span class="s">"interesting"</span><span class="p">])</span>
 215 <span class="go">somewhat</span>
 216
 217 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">attributes</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">"hello"</span><span class="p">))</span>
 218 <span class="go">None</span>
 219
 220 <span class="gp">&gt;&gt;&gt; </span><span class="n">attributes</span><span class="p">[</span><span class="s">"hello"</span><span class="p">]</span> <span class="o">=</span> <span class="s">"Guten Tag"</span>
 221 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">attributes</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">"hello"</span><span class="p">))</span>
 222 <span class="go">Guten Tag</span>
 223 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">"hello"</span><span class="p">))</span>
 224 <span class="go">Guten Tag</span>
 225 </pre></div>
 226 </div>
 227 <div class="section" id="elements-contain-text">
 228 <h2>Elements contain text</h2>
 229 <p>Elements can contain text:</p>
 230 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"root"</span><span class="p">)</span>
 231 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="o">.</span><span class="n">text</span> <span class="o">=</span> <span class="s">"TEXT"</span>
 232
 233 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">text</span><span class="p">)</span>
 234 <span class="go">TEXT</span>
 235
 236 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 237 <span class="go">b'&lt;root&gt;TEXT&lt;/root&gt;'</span>
 238 </pre></div>
 239 <p>In many XML documents (<em>data-centric</em> documents), this is the only place where
 240 text can be found.  It is encapsulated by a leaf tag at the very bottom of the
 241 tree hierarchy.</p>
 242 <p>However, if XML is used for tagged text documents such as (X)HTML, text can
 243 also appear between different elements, right in the middle of the tree:</p>
 244 <div class="syntax"><pre><span class="nt">&lt;html&gt;&lt;body&gt;</span>Hello<span class="nt">&lt;br/&gt;</span>World<span class="nt">&lt;/body&gt;&lt;/html&gt;</span>
 245 </pre></div>
 246 <p>Here, the <tt class="docutils literal">&lt;br/&gt;</tt> tag is surrounded by text.  This is often referred to as
 247 <em>document-style</em> or <em>mixed-content</em> XML.  Elements support this through their
 248 <tt class="docutils literal">tail</tt> property.  It contains the text that directly follows the element, up
 249 to the next element in the XML tree:</p>
 250 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">html</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"html"</span><span class="p">)</span>
 251 <span class="gp">&gt;&gt;&gt; </span><span class="n">body</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">html</span><span class="p">,</span> <span class="s">"body"</span><span class="p">)</span>
 252 <span class="gp">&gt;&gt;&gt; </span><span class="n">body</span><span class="o">.</span><span class="n">text</span> <span class="o">=</span> <span class="s">"TEXT"</span>
 253
 254 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">html</span><span class="p">)</span>
 255 <span class="go">b'&lt;html&gt;&lt;body&gt;TEXT&lt;/body&gt;&lt;/html&gt;'</span>
 256
 257 <span class="gp">&gt;&gt;&gt; </span><span class="n">br</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">body</span><span class="p">,</span> <span class="s">"br"</span><span class="p">)</span>
 258 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">html</span><span class="p">)</span>
 259 <span class="go">b'&lt;html&gt;&lt;body&gt;TEXT&lt;br/&gt;&lt;/body&gt;&lt;/html&gt;'</span>
 260
 261 <span class="gp">&gt;&gt;&gt; </span><span class="n">br</span><span class="o">.</span><span class="n">tail</span> <span class="o">=</span> <span class="s">"TAIL"</span>
 262 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">html</span><span class="p">)</span>
 263 <span class="go">b'&lt;html&gt;&lt;body&gt;TEXT&lt;br/&gt;TAIL&lt;/body&gt;&lt;/html&gt;'</span>
 264 </pre></div>
 265 <p>The two properties <tt class="docutils literal">.text</tt> and <tt class="docutils literal">.tail</tt> are enough to represent any
 266 text content in an XML document.  This way, the ElementTree API does
 267 not require any <a class="reference external" href="http://www.w3.org/TR/DOM-Level-3-Core/core.html#ID-1312295772">special text nodes</a> in addition to the Element
 268 class, that tend to get in the way fairly often (as you might know
 269 from classic <a class="reference external" href="http://www.w3.org/TR/DOM-Level-3-Core/core.html">DOM</a> APIs).</p>
 270 <p>However, there are cases where the tail text also gets in the way.
 271 For example, when you serialise an Element from within the tree, you
 272 do not always want its tail text in the result (although you would
 273 still want the tail text of its children).  For this purpose, the
 274 <tt class="docutils literal">tostring()</tt> function accepts the keyword argument <tt class="docutils literal">with_tail</tt>:</p>
 275 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">br</span><span class="p">)</span>
 276 <span class="go">b'&lt;br/&gt;TAIL'</span>
 277 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">br</span><span class="p">,</span> <span class="n">with_tail</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span> <span class="c"># lxml.etree only!</span>
 278 <span class="go">b'&lt;br/&gt;'</span>
 279 </pre></div>
 280 <p>If you want to read <em>only</em> the text, i.e. without any intermediate
 281 tags, you have to recursively concatenate all <tt class="docutils literal">text</tt> and <tt class="docutils literal">tail</tt>
 282 attributes in the correct order.  Again, the <tt class="docutils literal">tostring()</tt> function
 283 comes to the rescue, this time using the <tt class="docutils literal">method</tt> keyword:</p>
 284 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">html</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s">"text"</span><span class="p">)</span>
 285 <span class="go">b'TEXTTAIL'</span>
 286 </pre></div>
 287 </div>
 288 <div class="section" id="using-xpath-to-find-text">
 289 <h2>Using XPath to find text</h2>
 290 <p>Another way to extract the text content of a tree is <a class="reference external" href="xpathxslt.html#xpath">XPath</a>, which
 291 also allows you to extract the separate text chunks into a list:</p>
 292 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">html</span><span class="o">.</span><span class="n">xpath</span><span class="p">(</span><span class="s">"string()"</span><span class="p">))</span> <span class="c"># lxml.etree only!</span>
 293 <span class="go">TEXTTAIL</span>
 294 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">html</span><span class="o">.</span><span class="n">xpath</span><span class="p">(</span><span class="s">"//text()"</span><span class="p">))</span> <span class="c"># lxml.etree only!</span>
 295 <span class="go">['TEXT', 'TAIL']</span>
 296 </pre></div>
 297 <p>If you want to use this more often, you can wrap it in a function:</p>
 298 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">build_text_list</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XPath</span><span class="p">(</span><span class="s">"//text()"</span><span class="p">)</span> <span class="c"># lxml.etree only!</span>
 299 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">build_text_list</span><span class="p">(</span><span class="n">html</span><span class="p">))</span>
 300 <span class="go">['TEXT', 'TAIL']</span>
 301 </pre></div>
 302 <p>Note that a string result returned by XPath is a special 'smart'
 303 object that knows about its origins.  You can ask it where it came
 304 from through its <tt class="docutils literal">getparent()</tt> method, just as you would with
 305 Elements:</p>
 306 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">texts</span> <span class="o">=</span> <span class="n">build_text_list</span><span class="p">(</span><span class="n">html</span><span class="p">)</span>
 307 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">texts</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span>
 308 <span class="go">TEXT</span>
 309 <span class="gp">&gt;&gt;&gt; </span><span class="n">parent</span> <span class="o">=</span> <span class="n">texts</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">getparent</span><span class="p">()</span>
 310 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">parent</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 311 <span class="go">body</span>
 312
 313 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">texts</span><span class="p">[</span><span class="mi">1</span><span class="p">])</span>
 314 <span class="go">TAIL</span>
 315 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">texts</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">getparent</span><span class="p">()</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 316 <span class="go">br</span>
 317 </pre></div>
 318 <p>You can also find out if it's normal text content or tail text:</p>
 319 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">texts</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">is_text</span><span class="p">)</span>
 320 <span class="go">True</span>
 321 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">texts</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">is_text</span><span class="p">)</span>
 322 <span class="go">False</span>
 323 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">texts</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">is_tail</span><span class="p">)</span>
 324 <span class="go">True</span>
 325 </pre></div>
 326 <p>While this works for the results of the <tt class="docutils literal">text()</tt> function, lxml will
 327 not tell you the origin of a string value that was constructed by the
 328 XPath functions <tt class="docutils literal">string()</tt> or <tt class="docutils literal">concat()</tt>:</p>
 329 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">stringify</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XPath</span><span class="p">(</span><span class="s">"string()"</span><span class="p">)</span>
 330 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">stringify</span><span class="p">(</span><span class="n">html</span><span class="p">))</span>
 331 <span class="go">TEXTTAIL</span>
 332 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">stringify</span><span class="p">(</span><span class="n">html</span><span class="p">)</span><span class="o">.</span><span class="n">getparent</span><span class="p">())</span>
 333 <span class="go">None</span>
 334 </pre></div>
 335 </div>
 336 <div class="section" id="tree-iteration">
 337 <h2>Tree iteration</h2>
 338 <p>For problems like the above, where you want to recursively traverse the tree
 339 and do something with its elements, tree iteration is a very convenient
 340 solution.  Elements provide a tree iterator for this purpose.  It yields
 341 elements in <em>document order</em>, i.e. in the order their tags would appear if you
 342 serialised the tree to XML:</p>
 343 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"root"</span><span class="p">)</span>
 344 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s">"child"</span><span class="p">)</span><span class="o">.</span><span class="n">text</span> <span class="o">=</span> <span class="s">"Child 1"</span>
 345 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s">"child"</span><span class="p">)</span><span class="o">.</span><span class="n">text</span> <span class="o">=</span> <span class="s">"Child 2"</span>
 346 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s">"another"</span><span class="p">)</span><span class="o">.</span><span class="n">text</span> <span class="o">=</span> <span class="s">"Child 3"</span>
 347
 348 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 349 <span class="go">&lt;root&gt;</span>
 350 <span class="go">  &lt;child&gt;Child 1&lt;/child&gt;</span>
 351 <span class="go">  &lt;child&gt;Child 2&lt;/child&gt;</span>
 352 <span class="go">  &lt;another&gt;Child 3&lt;/another&gt;</span>
 353 <span class="go">&lt;/root&gt;</span>
 354
 355 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">iter</span><span class="p">():</span>
 356 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%s</span><span class="s"> - </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">element</span><span class="o">.</span><span class="n">tag</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">))</span>
 357 <span class="go">root - None</span>
 358 <span class="go">child - Child 1</span>
 359 <span class="go">child - Child 2</span>
 360 <span class="go">another - Child 3</span>
 361 </pre></div>
 362 <p>If you know you are only interested in a single tag, you can pass its name to
 363 <tt class="docutils literal">iter()</tt> to have it filter for you:</p>
 364 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">iter</span><span class="p">(</span><span class="s">"child"</span><span class="p">):</span>
 365 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%s</span><span class="s"> - </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">element</span><span class="o">.</span><span class="n">tag</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">))</span>
 366 <span class="go">child - Child 1</span>
 367 <span class="go">child - Child 2</span>
 368 </pre></div>
 369 <p>By default, iteration yields all nodes in the tree, including
 370 ProcessingInstructions, Comments and Entity instances.  If you want to
 371 make sure only Element objects are returned, you can pass the
 372 <tt class="docutils literal">Element</tt> factory as tag parameter:</p>
 373 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">Entity</span><span class="p">(</span><span class="s">"#234"</span><span class="p">))</span>
 374 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">Comment</span><span class="p">(</span><span class="s">"some comment"</span><span class="p">))</span>
 375
 376 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">iter</span><span class="p">():</span>
 377 <span class="gp">... </span>    <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">element</span><span class="o">.</span><span class="n">tag</span><span class="p">,</span> <span class="nb">basestring</span><span class="p">):</span>
 378 <span class="gp">... </span>        <span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%s</span><span class="s"> - </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">element</span><span class="o">.</span><span class="n">tag</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">))</span>
 379 <span class="gp">... </span>    <span class="k">else</span><span class="p">:</span>
 380 <span class="gp">... </span>        <span class="k">print</span><span class="p">(</span><span class="s">"SPECIAL: </span><span class="si">%s</span><span class="s"> - </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">element</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">))</span>
 381 <span class="go">root - None</span>
 382 <span class="go">child - Child 1</span>
 383 <span class="go">child - Child 2</span>
 384 <span class="go">another - Child 3</span>
 385 <span class="go">SPECIAL: &amp;#234; - &amp;#234;</span>
 386 <span class="go">SPECIAL: &lt;!--some comment--&gt; - some comment</span>
 387
 388 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">iter</span><span class="p">(</span><span class="n">tag</span><span class="o">=</span><span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">):</span>
 389 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%s</span><span class="s"> - </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">element</span><span class="o">.</span><span class="n">tag</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">))</span>
 390 <span class="go">root - None</span>
 391 <span class="go">child - Child 1</span>
 392 <span class="go">child - Child 2</span>
 393 <span class="go">another - Child 3</span>
 394
 395 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">iter</span><span class="p">(</span><span class="n">tag</span><span class="o">=</span><span class="n">etree</span><span class="o">.</span><span class="n">Entity</span><span class="p">):</span>
 396 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">)</span>
 397 <span class="go">&amp;#234;</span>
 398 </pre></div>
 399 <p>In lxml.etree, elements provide <a class="reference external" href="api.html#iteration">further iterators</a> for all directions in the
 400 tree: children, parents (or rather ancestors) and siblings.</p>
 401 </div>
 402 <div class="section" id="serialisation">
 403 <h2>Serialisation</h2>
 404 <p>Serialisation commonly uses the <tt class="docutils literal">tostring()</tt> function that returns a
 405 string, or the <tt class="docutils literal">ElementTree.write()</tt> method that writes to a file, a
 406 file-like object, or a URL (via FTP PUT or HTTP POST).  Both calls accept
 407 the same keyword arguments like <tt class="docutils literal">pretty_print</tt> for formatted output
 408 or <tt class="docutils literal">encoding</tt> to select a specific output encoding other than plain
 409 ASCII:</p>
 410 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</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">'&lt;root&gt;&lt;a&gt;&lt;b/&gt;&lt;/a&gt;&lt;/root&gt;'</span><span class="p">)</span>
 411
 412 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 413 <span class="go">b'&lt;root&gt;&lt;a&gt;&lt;b/&gt;&lt;/a&gt;&lt;/root&gt;'</span>
 414
 415 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">xml_declaration</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 416 <span class="go">&lt;?xml version='1.0' encoding='ASCII'?&gt;</span>
 417 <span class="go">&lt;root&gt;&lt;a&gt;&lt;b/&gt;&lt;/a&gt;&lt;/root&gt;</span>
 418
 419 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">encoding</span><span class="o">=</span><span class="s">'iso-8859-1'</span><span class="p">))</span>
 420 <span class="go">&lt;?xml version='1.0' encoding='iso-8859-1'?&gt;</span>
 421 <span class="go">&lt;root&gt;&lt;a&gt;&lt;b/&gt;&lt;/a&gt;&lt;/root&gt;</span>
 422
 423 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 424 <span class="go">&lt;root&gt;</span>
 425 <span class="go">  &lt;a&gt;</span>
 426 <span class="go">    &lt;b/&gt;</span>
 427 <span class="go">  &lt;/a&gt;</span>
 428 <span class="go">&lt;/root&gt;</span>
 429 </pre></div>
 430 <p>Note that pretty printing appends a newline at the end.</p>
 431 <p>Since lxml 2.0 (and ElementTree 1.3), the serialisation functions can
 432 do more than XML serialisation.  You can serialise to HTML or extract
 433 the text content by passing the <tt class="docutils literal">method</tt> keyword:</p>
 434 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span>
 435 <span class="gp">... </span>   <span class="s">'&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Hello&lt;br/&gt;World&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;'</span><span class="p">)</span>
 436
 437 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span> <span class="c"># default: method = 'xml'</span>
 438 <span class="go">b'&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Hello&lt;br/&gt;World&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;'</span>
 439
 440 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s">'xml'</span><span class="p">)</span> <span class="c"># same as above</span>
 441 <span class="go">b'&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Hello&lt;br/&gt;World&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;'</span>
 442
 443 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s">'html'</span><span class="p">)</span>
 444 <span class="go">b'&lt;html&gt;&lt;head&gt;&lt;/head&gt;&lt;body&gt;&lt;p&gt;Hello&lt;br&gt;World&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;'</span>
 445
 446 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s">'html'</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 447 <span class="go">&lt;html&gt;</span>
 448 <span class="go">&lt;head&gt;&lt;/head&gt;</span>
 449 <span class="go">&lt;body&gt;&lt;p&gt;Hello&lt;br&gt;World&lt;/p&gt;&lt;/body&gt;</span>
 450 <span class="go">&lt;/html&gt;</span>
 451
 452 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s">'text'</span><span class="p">)</span>
 453 <span class="go">b'HelloWorld'</span>
 454 </pre></div>
 455 <p>As for XML serialisation, the default encoding for plain text
 456 serialisation is ASCII:</p>
 457 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">br</span> <span class="o">=</span> <span class="n">root</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="s">'.//br'</span><span class="p">)</span>
 458 <span class="gp">&gt;&gt;&gt; </span><span class="n">br</span><span class="o">.</span><span class="n">tail</span> <span class="o">=</span> <span class="s">u'W</span><span class="se">\xf6</span><span class="s">rld'</span>
 459
 460 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s">'text'</span><span class="p">)</span>  <span class="c"># doctest: +ELLIPSIS</span>
 461 <span class="gt">Traceback (most recent call last):</span>
 462   <span class="c">...</span>
 463 <span class="gr">UnicodeEncodeError</span>: <span class="n">'ascii' codec can't encode character u'\xf6' ...</span>
 464
 465 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s">'text'</span><span class="p">,</span> <span class="n">encoding</span><span class="o">=</span><span class="s">"UTF-8"</span><span class="p">)</span>
 466 <span class="go">b'HelloW\xc3\xb6rld'</span>
 467 </pre></div>
 468 <p>Here, serialising to a Python unicode string instead of a byte string
 469 might become handy.  Just pass the <tt class="docutils literal">unicode</tt> type as encoding:</p>
 470 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="n">encoding</span><span class="o">=</span><span class="nb">unicode</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s">'text'</span><span class="p">)</span>
 471 <span class="go">u'HelloW\xf6rld'</span>
 472 </pre></div>
 473 <p>The W3C has a good <a class="reference external" href="http://www.w3.org/International/tutorials/tutorial-char-enc/">article about the Unicode character set and
 474 character encodings</a>.</p>
 475 </div>
 476 </div>
 477 <div class="section" id="the-elementtree-class">
 478 <h1>The ElementTree class</h1>
 479 <p>An <tt class="docutils literal">ElementTree</tt> is mainly a document wrapper around a tree with a
 480 root node.  It provides a couple of methods for parsing, serialisation
 481 and general document handling.  One of the bigger differences is that
 482 it serialises as a complete document, as opposed to a single
 483 <tt class="docutils literal">Element</tt>.  This includes top-level processing instructions and
 484 comments, as well as a DOCTYPE and other DTD content in the document:</p>
 485 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">tree</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">parse</span><span class="p">(</span><span class="n">StringIO</span><span class="p">(</span><span class="s">'''</span><span class="se">\</span>
 486 <span class="gp">... </span><span class="s">&lt;?xml version="1.0"?&gt;</span>
 487 <span class="gp">... </span><span class="s">&lt;!DOCTYPE root SYSTEM "test" [ &lt;!ENTITY tasty "eggs"&gt; ]&gt;</span>
 488 <span class="gp">... </span><span class="s">&lt;root&gt;</span>
 489 <span class="gp">... </span><span class="s">  &lt;a&gt;&amp;tasty;&lt;/a&gt;</span>
 490 <span class="gp">... </span><span class="s">&lt;/root&gt;</span>
 491 <span class="gp">... </span><span class="s">'''</span><span class="p">))</span>
 492
 493 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">tree</span><span class="o">.</span><span class="n">docinfo</span><span class="o">.</span><span class="n">doctype</span><span class="p">)</span>
 494 <span class="go">&lt;!DOCTYPE root SYSTEM "test"&gt;</span>
 495
 496 <span class="gp">&gt;&gt;&gt; </span><span class="c"># lxml 1.3.4 and later</span>
 497 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">tree</span><span class="p">))</span>
 498 <span class="go">&lt;!DOCTYPE root SYSTEM "test" [</span>
 499 <span class="go">&lt;!ENTITY tasty "eggs"&gt;</span>
 500 <span class="go">]&gt;</span>
 501 <span class="go">&lt;root&gt;</span>
 502 <span class="go">  &lt;a&gt;eggs&lt;/a&gt;</span>
 503 <span class="go">&lt;/root&gt;</span>
 504
 505 <span class="gp">&gt;&gt;&gt; </span><span class="c"># lxml 1.3.4 and later</span>
 506 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">ElementTree</span><span class="p">(</span><span class="n">tree</span><span class="o">.</span><span class="n">getroot</span><span class="p">())))</span>
 507 <span class="go">&lt;!DOCTYPE root SYSTEM "test" [</span>
 508 <span class="go">&lt;!ENTITY tasty "eggs"&gt;</span>
 509 <span class="go">]&gt;</span>
 510 <span class="go">&lt;root&gt;</span>
 511 <span class="go">  &lt;a&gt;eggs&lt;/a&gt;</span>
 512 <span class="go">&lt;/root&gt;</span>
 513
 514 <span class="gp">&gt;&gt;&gt; </span><span class="c"># ElementTree and lxml &lt;= 1.3.3</span>
 515 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">tree</span><span class="o">.</span><span class="n">getroot</span><span class="p">()))</span>
 516 <span class="go">&lt;root&gt;</span>
 517 <span class="go">  &lt;a&gt;eggs&lt;/a&gt;</span>
 518 <span class="go">&lt;/root&gt;</span>
 519 </pre></div>
 520 <p>Note that this has changed in lxml 1.3.4 to match the behaviour of
 521 lxml 2.0.  Before, the examples were serialised without DTD content,
 522 which made lxml loose DTD information in an input-output cycle.</p>
 523 </div>
 524 <div class="section" id="parsing-from-strings-and-files">
 525 <h1>Parsing from strings and files</h1>
 526 <p><tt class="docutils literal">lxml.etree</tt> supports parsing XML in a number of ways and from all
 527 important sources, namely strings, files, URLs (http/ftp) and
 528 file-like objects.  The main parse functions are <tt class="docutils literal">fromstring()</tt> and
 529 <tt class="docutils literal">parse()</tt>, both called with the source as first argument.  By
 530 default, they use the standard parser, but you can always pass a
 531 different parser as second argument.</p>
 532 <div class="section" id="the-fromstring-function">
 533 <h2>The fromstring() function</h2>
 534 <p>The <tt class="docutils literal">fromstring()</tt> function is the easiest way to parse a string:</p>
 535 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">some_xml_data</span> <span class="o">=</span> <span class="s">"&lt;root&gt;data&lt;/root&gt;"</span>
 536
 537 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">fromstring</span><span class="p">(</span><span class="n">some_xml_data</span><span class="p">)</span>
 538 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 539 <span class="go">root</span>
 540 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 541 <span class="go">b'&lt;root&gt;data&lt;/root&gt;'</span>
 542 </pre></div>
 543 </div>
 544 <div class="section" id="the-xml-function">
 545 <h2>The XML() function</h2>
 546 <p>The <tt class="docutils literal">XML()</tt> function behaves like the <tt class="docutils literal">fromstring()</tt> function, but is
 547 commonly used to write XML literals right into the source:</p>
 548 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</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">"&lt;root&gt;data&lt;/root&gt;"</span><span class="p">)</span>
 549 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 550 <span class="go">root</span>
 551 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 552 <span class="go">b'&lt;root&gt;data&lt;/root&gt;'</span>
 553 </pre></div>
 554 </div>
 555 <div class="section" id="the-parse-function">
 556 <h2>The parse() function</h2>
 557 <p>The <tt class="docutils literal">parse()</tt> function is used to parse from files and file-like objects:</p>
 558 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">some_file_like</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">(</span><span class="s">"&lt;root&gt;data&lt;/root&gt;"</span><span class="p">)</span>
 559
 560 <span class="gp">&gt;&gt;&gt; </span><span class="n">tree</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">parse</span><span class="p">(</span><span class="n">some_file_like</span><span class="p">)</span>
 561
 562 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">tree</span><span class="p">)</span>
 563 <span class="go">b'&lt;root&gt;data&lt;/root&gt;'</span>
 564 </pre></div>
 565 <p>Note that <tt class="docutils literal">parse()</tt> returns an ElementTree object, not an Element object as
 566 the string parser functions:</p>
 567 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">tree</span><span class="o">.</span><span class="n">getroot</span><span class="p">()</span>
 568 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 569 <span class="go">root</span>
 570 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 571 <span class="go">b'&lt;root&gt;data&lt;/root&gt;'</span>
 572 </pre></div>
 573 <p>The reasoning behind this difference is that <tt class="docutils literal">parse()</tt> returns a
 574 complete document from a file, while the string parsing functions are
 575 commonly used to parse XML fragments.</p>
 576 <p>The <tt class="docutils literal">parse()</tt> function supports any of the following sources:</p>
 577 <ul class="simple">
 578 <li>an open file object</li>
 579 <li>a file-like object that has a <tt class="docutils literal">.read(byte_count)</tt> method returning
 580 a byte string on each call</li>
 581 <li>a filename string</li>
 582 <li>an HTTP or FTP URL string</li>
 583 </ul>
 584 <p>Note that passing a filename or URL is usually faster than passing an
 585 open file.</p>
 586 </div>
 587 <div class="section" id="parser-objects">
 588 <h2>Parser objects</h2>
 589 <p>By default, <tt class="docutils literal">lxml.etree</tt> uses a standard parser with a default setup.  If
 590 you want to configure the parser, you can create a you instance:</p>
 591 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </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">remove_blank_text</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span> <span class="c"># lxml.etree only!</span>
 592 </pre></div>
 593 <p>This creates a parser that removes empty text between tags while parsing,
 594 which can reduce the size of the tree and avoid dangling tail text if you know
 595 that whitespace-only content is not meaningful for your data.  An example:</p>
 596 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</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">"&lt;root&gt;  &lt;a/&gt;   &lt;b&gt;  &lt;/b&gt;     &lt;/root&gt;"</span><span class="p">,</span> <span class="n">parser</span><span class="p">)</span>
 597
 598 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 599 <span class="go">b'&lt;root&gt;&lt;a/&gt;&lt;b&gt;  &lt;/b&gt;&lt;/root&gt;'</span>
 600 </pre></div>
 601 <p>Note that the whitespace content inside the <tt class="docutils literal">&lt;b&gt;</tt> tag was not removed, as
 602 content at leaf elements tends to be data content (even if blank).  You can
 603 easily remove it in an additional step by traversing the tree:</p>
 604 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">iter</span><span class="p">(</span><span class="s">"*"</span><span class="p">):</span>
 605 <span class="gp">... </span>    <span class="k">if</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span> <span class="ow">is</span> <span class="ow">not</span> <span class="bp">None</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="o">.</span><span class="n">strip</span><span class="p">():</span>
 606 <span class="gp">... </span>        <span class="n">element</span><span class="o">.</span><span class="n">text</span> <span class="o">=</span> <span class="bp">None</span>
 607
 608 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 609 <span class="go">b'&lt;root&gt;&lt;a/&gt;&lt;b/&gt;&lt;/root&gt;'</span>
 610 </pre></div>
 611 <p>See <tt class="docutils literal">help(etree.XMLParser)</tt> to find out about the available parser options.</p>
 612 </div>
 613 <div class="section" id="incremental-parsing">
 614 <h2>Incremental parsing</h2>
 615 <p><tt class="docutils literal">lxml.etree</tt> provides two ways for incremental step-by-step parsing.  One is
 616 through file-like objects, where it calls the <tt class="docutils literal">read()</tt> method repeatedly.
 617 This is best used where the data arrives from a source like <tt class="docutils literal">urllib</tt> or any
 618 other file-like object that can provide data on request.  Note that the parser
 619 will block and wait until data becomes available in this case:</p>
 620 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">DataSource</span><span class="p">:</span>
 621 <span class="gp">... </span>    <span class="n">data</span> <span class="o">=</span> <span class="p">[</span> <span class="n">b</span><span class="s">"&lt;roo"</span><span class="p">,</span> <span class="n">b</span><span class="s">"t&gt;&lt;"</span><span class="p">,</span> <span class="n">b</span><span class="s">"a/"</span><span class="p">,</span> <span class="n">b</span><span class="s">"&gt;&lt;"</span><span class="p">,</span> <span class="n">b</span><span class="s">"/root&gt;"</span> <span class="p">]</span>
 622 <span class="gp">... </span>    <span class="k">def</span> <span class="nf">read</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">requested_size</span><span class="p">):</span>
 623 <span class="gp">... </span>        <span class="k">try</span><span class="p">:</span>
 624 <span class="gp">... </span>            <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="o">.</span><span class="n">pop</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
 625 <span class="gp">... </span>        <span class="k">except</span> <span class="ne">IndexError</span><span class="p">:</span>
 626 <span class="gp">... </span>            <span class="k">return</span> <span class="n">b</span><span class="s">''</span>
 627
 628 <span class="gp">&gt;&gt;&gt; </span><span class="n">tree</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">parse</span><span class="p">(</span><span class="n">DataSource</span><span class="p">())</span>
 629
 630 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">tree</span><span class="p">)</span>
 631 <span class="go">b'&lt;root&gt;&lt;a/&gt;&lt;/root&gt;'</span>
 632 </pre></div>
 633 <p>The second way is through a feed parser interface, given by the <tt class="docutils literal">feed(data)</tt>
 634 and <tt class="docutils literal">close()</tt> methods:</p>
 635 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </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>
 636
 637 <span class="gp">&gt;&gt;&gt; </span><span class="n">parser</span><span class="o">.</span><span class="n">feed</span><span class="p">(</span><span class="s">"&lt;roo"</span><span class="p">)</span>
 638 <span class="gp">&gt;&gt;&gt; </span><span class="n">parser</span><span class="o">.</span><span class="n">feed</span><span class="p">(</span><span class="s">"t&gt;&lt;"</span><span class="p">)</span>
 639 <span class="gp">&gt;&gt;&gt; </span><span class="n">parser</span><span class="o">.</span><span class="n">feed</span><span class="p">(</span><span class="s">"a/"</span><span class="p">)</span>
 640 <span class="gp">&gt;&gt;&gt; </span><span class="n">parser</span><span class="o">.</span><span class="n">feed</span><span class="p">(</span><span class="s">"&gt;&lt;"</span><span class="p">)</span>
 641 <span class="gp">&gt;&gt;&gt; </span><span class="n">parser</span><span class="o">.</span><span class="n">feed</span><span class="p">(</span><span class="s">"/root&gt;"</span><span class="p">)</span>
 642
 643 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
 644
 645 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 646 <span class="go">b'&lt;root&gt;&lt;a/&gt;&lt;/root&gt;'</span>
 647 </pre></div>
 648 <p>Here, you can interrupt the parsing process at any time and continue it later
 649 on with another call to the <tt class="docutils literal">feed()</tt> method.  This comes in handy if you
 650 want to avoid blocking calls to the parser, e.g. in frameworks like Twisted,
 651 or whenever data comes in slowly or in chunks and you want to do other things
 652 while waiting for the next chunk.</p>
 653 <p>After calling the <tt class="docutils literal">close()</tt> method (or when an exception was raised
 654 by the parser), you can reuse the parser by calling its <tt class="docutils literal">feed()</tt>
 655 method again:</p>
 656 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">parser</span><span class="o">.</span><span class="n">feed</span><span class="p">(</span><span class="s">"&lt;root/&gt;"</span><span class="p">)</span>
 657 <span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
 658 <span class="gp">&gt;&gt;&gt; </span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
 659 <span class="go">b'&lt;root/&gt;'</span>
 660 </pre></div>
 661 </div>
 662 <div class="section" id="event-driven-parsing">
 663 <h2>Event-driven parsing</h2>
 664 <p>Sometimes, all you need from a document is a small fraction somewhere deep
 665 inside the tree, so parsing the whole tree into memory, traversing it and
 666 dropping it can be too much overhead.  <tt class="docutils literal">lxml.etree</tt> supports this use case
 667 with two event-driven parser interfaces, one that generates parser events
 668 while building the tree (<tt class="docutils literal">iterparse</tt>), and one that does not build the tree
 669 at all, and instead calls feedback methods on a target object in a SAX-like
 670 fashion.</p>
 671 <p>Here is a simple <tt class="docutils literal">iterparse()</tt> example:</p>
 672 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">some_file_like</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">(</span><span class="s">"&lt;root&gt;&lt;a&gt;data&lt;/a&gt;&lt;/root&gt;"</span><span class="p">)</span>
 673
 674 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">event</span><span class="p">,</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">etree</span><span class="o">.</span><span class="n">iterparse</span><span class="p">(</span><span class="n">some_file_like</span><span class="p">):</span>
 675 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%s</span><span class="s">, </span><span class="si">%4s</span><span class="s">, </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">event</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">tag</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">))</span>
 676 <span class="go">end,    a, data</span>
 677 <span class="go">end, root, None</span>
 678 </pre></div>
 679 <p>By default, <tt class="docutils literal">iterparse()</tt> only generates events when it is done parsing an
 680 element, but you can control this through the <tt class="docutils literal">events</tt> keyword argument:</p>
 681 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">some_file_like</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">(</span><span class="s">"&lt;root&gt;&lt;a&gt;data&lt;/a&gt;&lt;/root&gt;"</span><span class="p">)</span>
 682
 683 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">event</span><span class="p">,</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">etree</span><span class="o">.</span><span class="n">iterparse</span><span class="p">(</span><span class="n">some_file_like</span><span class="p">,</span>
 684 <span class="gp">... </span>                                      <span class="n">events</span><span class="o">=</span><span class="p">(</span><span class="s">"start"</span><span class="p">,</span> <span class="s">"end"</span><span class="p">)):</span>
 685 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%5s</span><span class="s">, </span><span class="si">%4s</span><span class="s">, </span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">event</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">tag</span><span class="p">,</span> <span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">))</span>
 686 <span class="go">start, root, None</span>
 687 <span class="go">start,    a, data</span>
 688 <span class="go">  end,    a, data</span>
 689 <span class="go">  end, root, None</span>
 690 </pre></div>
 691 <p>Note that the text, tail and children of an Element are not necessarily there
 692 yet when receiving the <tt class="docutils literal">start</tt> event.  Only the <tt class="docutils literal">end</tt> event guarantees
 693 that the Element has been parsed completely.</p>
 694 <p>It also allows to <tt class="docutils literal">.clear()</tt> or modify the content of an Element to
 695 save memory. So if you parse a large tree and you want to keep memory
 696 usage small, you should clean up parts of the tree that you no longer
 697 need:</p>
 698 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">some_file_like</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">(</span>
 699 <span class="gp">... </span>    <span class="s">"&lt;root&gt;&lt;a&gt;&lt;b&gt;data&lt;/b&gt;&lt;/a&gt;&lt;a&gt;&lt;b/&gt;&lt;/a&gt;&lt;/root&gt;"</span><span class="p">)</span>
 700
 701 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">event</span><span class="p">,</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">etree</span><span class="o">.</span><span class="n">iterparse</span><span class="p">(</span><span class="n">some_file_like</span><span class="p">):</span>
 702 <span class="gp">... </span>    <span class="k">if</span> <span class="n">element</span><span class="o">.</span><span class="n">tag</span> <span class="o">==</span> <span class="s">'b'</span><span class="p">:</span>
 703 <span class="gp">... </span>        <span class="k">print</span><span class="p">(</span><span class="n">element</span><span class="o">.</span><span class="n">text</span><span class="p">)</span>
 704 <span class="gp">... </span>    <span class="k">elif</span> <span class="n">element</span><span class="o">.</span><span class="n">tag</span> <span class="o">==</span> <span class="s">'a'</span><span class="p">:</span>
 705 <span class="gp">... </span>        <span class="k">print</span><span class="p">(</span><span class="s">"** cleaning up the subtree"</span><span class="p">)</span>
 706 <span class="gp">... </span>        <span class="n">element</span><span class="o">.</span><span class="n">clear</span><span class="p">()</span>
 707 <span class="go">data</span>
 708 <span class="go">** cleaning up the subtree</span>
 709 <span class="go">None</span>
 710 <span class="go">** cleaning up the subtree</span>
 711 </pre></div>
 712 <p>A very important use cases for <tt class="docutils literal">iterparse()</tt> is parsing large
 713 generated XML files, e.g. database dumps.  Most often, these XML
 714 formats only have one main data item element that hangs directly below
 715 the root node and that is repeated thousands of times.  In this case,
 716 it is best practice to let <tt class="docutils literal">lxml.etree</tt> do the tree building and to
 717 only intercept exactly on this one Element, using the normal tree API
 718 for data extraction.</p>
 719 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">xml_file</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">(</span><span class="s">'''</span><span class="se">\</span>
 720 <span class="gp">... </span><span class="s">&lt;root&gt;</span>
 721 <span class="gp">... </span><span class="s">  &lt;a&gt;&lt;b&gt;ABC&lt;/b&gt;&lt;c&gt;abc&lt;/c&gt;&lt;/a&gt;</span>
 722 <span class="gp">... </span><span class="s">  &lt;a&gt;&lt;b&gt;MORE DATA&lt;/b&gt;&lt;c&gt;more data&lt;/c&gt;&lt;/a&gt;</span>
 723 <span class="gp">... </span><span class="s">  &lt;a&gt;&lt;b&gt;XYZ&lt;/b&gt;&lt;c&gt;xyz&lt;/c&gt;&lt;/a&gt;</span>
 724 <span class="gp">... </span><span class="s">&lt;/root&gt;'''</span><span class="p">)</span>
 725
 726 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">_</span><span class="p">,</span> <span class="n">element</span> <span class="ow">in</span> <span class="n">etree</span><span class="o">.</span><span class="n">iterparse</span><span class="p">(</span><span class="n">xml_file</span><span class="p">,</span> <span class="n">tag</span><span class="o">=</span><span class="s">'a'</span><span class="p">):</span>
 727 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="s">'</span><span class="si">%s</span><span class="s"> -- </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">element</span><span class="o">.</span><span class="n">findtext</span><span class="p">(</span><span class="s">'b'</span><span class="p">),</span> <span class="n">element</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">text</span><span class="p">))</span>
 728 <span class="gp">... </span>    <span class="n">element</span><span class="o">.</span><span class="n">clear</span><span class="p">()</span>
 729 <span class="go">ABC -- abc</span>
 730 <span class="go">MORE DATA -- more data</span>
 731 <span class="go">XYZ -- xyz</span>
 732 </pre></div>
 733 <p>If, for some reason, building the tree is not desired at all, the
 734 target parser interface of <tt class="docutils literal">lxml.etree</tt> can be used.  It creates
 735 SAX-like events by calling the methods of a target object.  By
 736 implementing some or all of these methods, you can control which
 737 events are generated:</p>
 738 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">ParserTarget</span><span class="p">:</span>
 739 <span class="gp">... </span>    <span class="n">events</span> <span class="o">=</span> <span class="p">[]</span>
 740 <span class="gp">... </span>    <span class="n">close_count</span> <span class="o">=</span> <span class="mi">0</span>
 741 <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>
 742 <span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">events</span><span class="o">.</span><span class="n">append</span><span class="p">((</span><span class="s">"start"</span><span class="p">,</span> <span class="n">tag</span><span class="p">,</span> <span class="n">attrib</span><span class="p">))</span>
 743 <span class="gp">... </span>    <span class="k">def</span> <span class="nf">close</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
 744 <span class="gp">... </span>        <span class="n">events</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">events</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">events</span><span class="p">,</span> <span class="p">[]</span>
 745 <span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">close_count</span> <span class="o">+=</span> <span class="mi">1</span>
 746 <span class="gp">... </span>        <span class="k">return</span> <span class="n">events</span>
 747
 748 <span class="gp">&gt;&gt;&gt; </span><span class="n">parser_target</span> <span class="o">=</span> <span class="n">ParserTarget</span><span class="p">()</span>
 749
 750 <span class="gp">&gt;&gt;&gt; </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">parser_target</span><span class="p">)</span>
 751 <span class="gp">&gt;&gt;&gt; </span><span class="n">events</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">fromstring</span><span class="p">(</span><span class="s">'&lt;root test="true"/&gt;'</span><span class="p">,</span> <span class="n">parser</span><span class="p">)</span>
 752
 753 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">parser_target</span><span class="o">.</span><span class="n">close_count</span><span class="p">)</span>
 754 <span class="go">1</span>
 755
 756 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">event</span> <span class="ow">in</span> <span class="n">events</span><span class="p">:</span>
 757 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="s">'event: </span><span class="si">%s</span><span class="s"> - tag: </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">event</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="n">event</span><span class="p">[</span><span class="mi">1</span><span class="p">]))</span>
 758 <span class="gp">... </span>    <span class="k">for</span> <span class="n">attr</span><span class="p">,</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">event</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
 759 <span class="gp">... </span>        <span class="k">print</span><span class="p">(</span><span class="s">' * </span><span class="si">%s</span><span class="s"> = </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">attr</span><span class="p">,</span> <span class="n">value</span><span class="p">))</span>
 760 <span class="go">event: start - tag: root</span>
 761 <span class="go"> * test = true</span>
 762 </pre></div>
 763 <p>You can reuse the parser and its target as often as you like, so you
 764 should take care that the <tt class="docutils literal">.close()</tt> methods really resets the
 765 target to a usable state (also in the case of an error!).</p>
 766 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">events</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">fromstring</span><span class="p">(</span><span class="s">'&lt;root test="true"/&gt;'</span><span class="p">,</span> <span class="n">parser</span><span class="p">)</span>
 767 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">parser_target</span><span class="o">.</span><span class="n">close_count</span><span class="p">)</span>
 768 <span class="go">2</span>
 769 <span class="gp">&gt;&gt;&gt; </span><span class="n">events</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">fromstring</span><span class="p">(</span><span class="s">'&lt;root test="true"/&gt;'</span><span class="p">,</span> <span class="n">parser</span><span class="p">)</span>
 770 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">parser_target</span><span class="o">.</span><span class="n">close_count</span><span class="p">)</span>
 771 <span class="go">3</span>
 772 <span class="gp">&gt;&gt;&gt; </span><span class="n">events</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">fromstring</span><span class="p">(</span><span class="s">'&lt;root test="true"/&gt;'</span><span class="p">,</span> <span class="n">parser</span><span class="p">)</span>
 773 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">parser_target</span><span class="o">.</span><span class="n">close_count</span><span class="p">)</span>
 774 <span class="go">4</span>
 775
 776 <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">event</span> <span class="ow">in</span> <span class="n">events</span><span class="p">:</span>
 777 <span class="gp">... </span>    <span class="k">print</span><span class="p">(</span><span class="s">'event: </span><span class="si">%s</span><span class="s"> - tag: </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">event</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="n">event</span><span class="p">[</span><span class="mi">1</span><span class="p">]))</span>
 778 <span class="gp">... </span>    <span class="k">for</span> <span class="n">attr</span><span class="p">,</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">event</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
 779 <span class="gp">... </span>        <span class="k">print</span><span class="p">(</span><span class="s">' * </span><span class="si">%s</span><span class="s"> = </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">attr</span><span class="p">,</span> <span class="n">value</span><span class="p">))</span>
 780 <span class="go">event: start - tag: root</span>
 781 <span class="go"> * test = true</span>
 782 </pre></div>
 783 </div>
 784 </div>
 785 <div class="section" id="namespaces">
 786 <h1>Namespaces</h1>
 787 <p>The ElementTree API avoids <a class="reference external" href="http://www.w3.org/TR/xml-names/#ns-qualnames">namespace prefixes</a> wherever possible and deploys
 788 the real namespaces instead:</p>
 789 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">xhtml</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">"{http://www.w3.org/1999/xhtml}html"</span><span class="p">)</span>
 790 <span class="gp">&gt;&gt;&gt; </span><span class="n">body</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">xhtml</span><span class="p">,</span> <span class="s">"{http://www.w3.org/1999/xhtml}body"</span><span class="p">)</span>
 791 <span class="gp">&gt;&gt;&gt; </span><span class="n">body</span><span class="o">.</span><span class="n">text</span> <span class="o">=</span> <span class="s">"Hello World"</span>
 792
 793 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">xhtml</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 794 <span class="go">&lt;html:html xmlns:html="http://www.w3.org/1999/xhtml"&gt;</span>
 795 <span class="go">  &lt;html:body&gt;Hello World&lt;/html:body&gt;</span>
 796 <span class="go">&lt;/html:html&gt;</span>
 797 </pre></div>
 798 <p>The notation that ElementTree uses was originally brought up by <a class="reference external" href="http://www.jclark.com/xml/xmlns.htm">James
 799 Clark</a>.  It has the major advantage of providing a universally
 800 qualified name for a tag, regardless of any prefixes that may or may
 801 not have been used or defined in a document.  By moving the
 802 indirection of prefixes out of the way, it makes namespace aware code
 803 much clearer and safer.</p>
 804 <p>As you can see from the example, prefixes only become important when
 805 you serialise the result.  However, the above code looks somewhat
 806 verbose due to the lengthy namespace names.  And retyping or copying a
 807 string over and over again is error prone.  It is therefore common
 808 practice to store a namespace URI in a global variable.  To adapt the
 809 namespace prefixes for serialisation, you can also pass a mapping to
 810 the Element factory function, e.g. to define the default namespace:</p>
 811 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">XHTML_NAMESPACE</span> <span class="o">=</span> <span class="s">"http://www.w3.org/1999/xhtml"</span>
 812 <span class="gp">&gt;&gt;&gt; </span><span class="n">XHTML</span> <span class="o">=</span> <span class="s">"{</span><span class="si">%s</span><span class="s">}"</span> <span class="o">%</span> <span class="n">XHTML_NAMESPACE</span>
 813
 814 <span class="gp">&gt;&gt;&gt; </span><span class="n">NSMAP</span> <span class="o">=</span> <span class="p">{</span><span class="bp">None</span> <span class="p">:</span> <span class="n">XHTML_NAMESPACE</span><span class="p">}</span> <span class="c"># the default namespace (no prefix)</span>
 815
 816 <span class="gp">&gt;&gt;&gt; </span><span class="n">xhtml</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="n">XHTML</span> <span class="o">+</span> <span class="s">"html"</span><span class="p">,</span> <span class="n">nsmap</span><span class="o">=</span><span class="n">NSMAP</span><span class="p">)</span> <span class="c"># lxml only!</span>
 817 <span class="gp">&gt;&gt;&gt; </span><span class="n">body</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">xhtml</span><span class="p">,</span> <span class="n">XHTML</span> <span class="o">+</span> <span class="s">"body"</span><span class="p">)</span>
 818 <span class="gp">&gt;&gt;&gt; </span><span class="n">body</span><span class="o">.</span><span class="n">text</span> <span class="o">=</span> <span class="s">"Hello World"</span>
 819
 820 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">xhtml</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 821 <span class="go">&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;</span>
 822 <span class="go">  &lt;body&gt;Hello World&lt;/body&gt;</span>
 823 <span class="go">&lt;/html&gt;</span>
 824 </pre></div>
 825 <p>lxml.etree allows you to look up the current namespaces defined for a
 826 node through the <tt class="docutils literal">.nsmap</tt> property:</p>
 827 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">xhtml</span><span class="o">.</span><span class="n">nsmap</span>
 828 <span class="go">{None: 'http://www.w3.org/1999/xhtml'}</span>
 829 </pre></div>
 830 <p>Note, however, that this includes all prefixes known in the context of
 831 an Element, not only those that it defines itself.</p>
 832 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">Element</span><span class="p">(</span><span class="s">'root'</span><span class="p">,</span> <span class="n">nsmap</span><span class="o">=</span><span class="p">{</span><span class="s">'a'</span><span class="p">:</span> <span class="s">'http://a.b/c'</span><span class="p">})</span>
 833 <span class="gp">&gt;&gt;&gt; </span><span class="n">child</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">SubElement</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s">'child'</span><span class="p">,</span>
 834 <span class="gp">... </span>                         <span class="n">nsmap</span><span class="o">=</span><span class="p">{</span><span class="s">'b'</span><span class="p">:</span> <span class="s">'http://b.c/d'</span><span class="p">})</span>
 835 <span class="gp">&gt;&gt;&gt; </span><span class="nb">len</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">nsmap</span><span class="p">)</span>
 836 <span class="go">1</span>
 837 <span class="gp">&gt;&gt;&gt; </span><span class="nb">len</span><span class="p">(</span><span class="n">child</span><span class="o">.</span><span class="n">nsmap</span><span class="p">)</span>
 838 <span class="go">2</span>
 839 <span class="gp">&gt;&gt;&gt; </span><span class="n">child</span><span class="o">.</span><span class="n">nsmap</span><span class="p">[</span><span class="s">'a'</span><span class="p">]</span>
 840 <span class="go">'http://a.b/c'</span>
 841 <span class="gp">&gt;&gt;&gt; </span><span class="n">child</span><span class="o">.</span><span class="n">nsmap</span><span class="p">[</span><span class="s">'b'</span><span class="p">]</span>
 842 <span class="go">'http://b.c/d'</span>
 843 </pre></div>
 844 <p>Therefore, modifying the returned dict cannot have any meaningful
 845 impact on the Element.  Any changes to it are ignored.</p>
 846 <p>Namespaces on attributes work alike, but since version 2.3, lxml.etree
 847 will make sure that the attribute uses a prefixed namespace
 848 declaration.  This is because unprefixed attribute names are not
 849 considered being in a namespace by the XML namespace specification
 850 (<a class="reference external" href="http://www.w3.org/TR/2009/REC-xml-names-20091208/#defaulting">section 6.2</a>), so they may end up loosing their namespace on a
 851 serialise-parse roundtrip, even if they appear in a namespaced
 852 element.</p>
 853 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">body</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="n">XHTML</span> <span class="o">+</span> <span class="s">"bgcolor"</span><span class="p">,</span> <span class="s">"#CCFFAA"</span><span class="p">)</span>
 854
 855 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">xhtml</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 856 <span class="go">&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;</span>
 857 <span class="go">  &lt;body xmlns:html="http://www.w3.org/1999/xhtml" html:bgcolor="#CCFFAA"&gt;Hello World&lt;/body&gt;</span>
 858 <span class="go">&lt;/html&gt;</span>
 859
 860 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">body</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">"bgcolor"</span><span class="p">))</span>
 861 <span class="go">None</span>
 862 <span class="gp">&gt;&gt;&gt; </span><span class="n">body</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">XHTML</span> <span class="o">+</span> <span class="s">"bgcolor"</span><span class="p">)</span>
 863 <span class="go">'#CCFFAA'</span>
 864 </pre></div>
 865 <p>You can also use XPath with fully qualified names:</p>
 866 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">find_xhtml_body</span> <span class="o">=</span> <span class="n">etree</span><span class="o">.</span><span class="n">ETXPath</span><span class="p">(</span>      <span class="c"># lxml only !</span>
 867 <span class="gp">... </span>    <span class="s">"//{</span><span class="si">%s</span><span class="s">}body"</span> <span class="o">%</span> <span class="n">XHTML_NAMESPACE</span><span class="p">)</span>
 868 <span class="gp">&gt;&gt;&gt; </span><span class="n">results</span> <span class="o">=</span> <span class="n">find_xhtml_body</span><span class="p">(</span><span class="n">xhtml</span><span class="p">)</span>
 869
 870 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">results</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 871 <span class="go">{http://www.w3.org/1999/xhtml}body</span>
 872 </pre></div>
 873 </div>
 874 <div class="section" id="the-e-factory">
 875 <h1>The E-factory</h1>
 876 <p>The <tt class="docutils literal"><span class="pre">E-factory</span></tt> provides a simple and compact syntax for generating XML and
 877 HTML:</p>
 878 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">lxml.builder</span> <span class="kn">import</span> <span class="n">E</span>
 879
 880 <span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">CLASS</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">):</span> <span class="c"># class is a reserved word in Python</span>
 881 <span class="gp">... </span>    <span class="k">return</span> <span class="p">{</span><span class="s">"class"</span><span class="p">:</span><span class="s">' '</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">args</span><span class="p">)}</span>
 882
 883 <span class="gp">&gt;&gt;&gt; </span><span class="n">html</span> <span class="o">=</span> <span class="n">page</span> <span class="o">=</span> <span class="p">(</span>
 884 <span class="gp">... </span>  <span class="n">E</span><span class="o">.</span><span class="n">html</span><span class="p">(</span>       <span class="c"># create an Element called "html"</span>
 885 <span class="gp">... </span>    <span class="n">E</span><span class="o">.</span><span class="n">head</span><span class="p">(</span>
 886 <span class="gp">... </span>      <span class="n">E</span><span class="o">.</span><span class="n">title</span><span class="p">(</span><span class="s">"This is a sample document"</span><span class="p">)</span>
 887 <span class="gp">... </span>    <span class="p">),</span>
 888 <span class="gp">... </span>    <span class="n">E</span><span class="o">.</span><span class="n">body</span><span class="p">(</span>
 889 <span class="gp">... </span>      <span class="n">E</span><span class="o">.</span><span class="n">h1</span><span class="p">(</span><span class="s">"Hello!"</span><span class="p">,</span> <span class="n">CLASS</span><span class="p">(</span><span class="s">"title"</span><span class="p">)),</span>
 890 <span class="gp">... </span>      <span class="n">E</span><span class="o">.</span><span class="n">p</span><span class="p">(</span><span class="s">"This is a paragraph with "</span><span class="p">,</span> <span class="n">E</span><span class="o">.</span><span class="n">b</span><span class="p">(</span><span class="s">"bold"</span><span class="p">),</span> <span class="s">" text in it!"</span><span class="p">),</span>
 891 <span class="gp">... </span>      <span class="n">E</span><span class="o">.</span><span class="n">p</span><span class="p">(</span><span class="s">"This is another paragraph, with a"</span><span class="p">,</span> <span class="s">"</span><span class="se">\n</span><span class="s">      "</span><span class="p">,</span>
 892 <span class="gp">... </span>        <span class="n">E</span><span class="o">.</span><span class="n">a</span><span class="p">(</span><span class="s">"link"</span><span class="p">,</span> <span class="n">href</span><span class="o">=</span><span class="s">"http://www.python.org"</span><span class="p">),</span> <span class="s">"."</span><span class="p">),</span>
 893 <span class="gp">... </span>      <span class="n">E</span><span class="o">.</span><span class="n">p</span><span class="p">(</span><span class="s">"Here are some reservered characters: &lt;spam&amp;egg&gt;."</span><span class="p">),</span>
 894 <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">"&lt;p&gt;And finally an embedded XHTML fragment.&lt;/p&gt;"</span><span class="p">),</span>
 895 <span class="gp">... </span>    <span class="p">)</span>
 896 <span class="gp">... </span>  <span class="p">)</span>
 897 <span class="gp">... </span><span class="p">)</span>
 898
 899 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">page</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 900 <span class="go">&lt;html&gt;</span>
 901 <span class="go">  &lt;head&gt;</span>
 902 <span class="go">    &lt;title&gt;This is a sample document&lt;/title&gt;</span>
 903 <span class="go">  &lt;/head&gt;</span>
 904 <span class="go">  &lt;body&gt;</span>
 905 <span class="go">    &lt;h1 class="title"&gt;Hello!&lt;/h1&gt;</span>
 906 <span class="go">    &lt;p&gt;This is a paragraph with &lt;b&gt;bold&lt;/b&gt; text in it!&lt;/p&gt;</span>
 907 <span class="go">    &lt;p&gt;This is another paragraph, with a</span>
 908 <span class="go">      &lt;a href="http://www.python.org"&gt;link&lt;/a&gt;.&lt;/p&gt;</span>
 909 <span class="go">    &lt;p&gt;Here are some reservered characters: &amp;lt;spam&amp;amp;egg&amp;gt;.&lt;/p&gt;</span>
 910 <span class="go">    &lt;p&gt;And finally an embedded XHTML fragment.&lt;/p&gt;</span>
 911 <span class="go">  &lt;/body&gt;</span>
 912 <span class="go">&lt;/html&gt;</span>
 913 </pre></div>
 914 <p>The Element creation based on attribute access makes it easy to build up a
 915 simple vocabulary for an XML language:</p>
 916 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">lxml.builder</span> <span class="kn">import</span> <span class="n">ElementMaker</span> <span class="c"># lxml only !</span>
 917
 918 <span class="gp">&gt;&gt;&gt; </span><span class="n">E</span> <span class="o">=</span> <span class="n">ElementMaker</span><span class="p">(</span><span class="n">namespace</span><span class="o">=</span><span class="s">"http://my.de/fault/namespace"</span><span class="p">,</span>
 919 <span class="gp">... </span>                 <span class="n">nsmap</span><span class="o">=</span><span class="p">{</span><span class="s">'p'</span> <span class="p">:</span> <span class="s">"http://my.de/fault/namespace"</span><span class="p">})</span>
 920
 921 <span class="gp">&gt;&gt;&gt; </span><span class="n">DOC</span> <span class="o">=</span> <span class="n">E</span><span class="o">.</span><span class="n">doc</span>
 922 <span class="gp">&gt;&gt;&gt; </span><span class="n">TITLE</span> <span class="o">=</span> <span class="n">E</span><span class="o">.</span><span class="n">title</span>
 923 <span class="gp">&gt;&gt;&gt; </span><span class="n">SECTION</span> <span class="o">=</span> <span class="n">E</span><span class="o">.</span><span class="n">section</span>
 924 <span class="gp">&gt;&gt;&gt; </span><span class="n">PAR</span> <span class="o">=</span> <span class="n">E</span><span class="o">.</span><span class="n">par</span>
 925
 926 <span class="gp">&gt;&gt;&gt; </span><span class="n">my_doc</span> <span class="o">=</span> <span class="n">DOC</span><span class="p">(</span>
 927 <span class="gp">... </span>  <span class="n">TITLE</span><span class="p">(</span><span class="s">"The dog and the hog"</span><span class="p">),</span>
 928 <span class="gp">... </span>  <span class="n">SECTION</span><span class="p">(</span>
 929 <span class="gp">... </span>    <span class="n">TITLE</span><span class="p">(</span><span class="s">"The dog"</span><span class="p">),</span>
 930 <span class="gp">... </span>    <span class="n">PAR</span><span class="p">(</span><span class="s">"Once upon a time, ..."</span><span class="p">),</span>
 931 <span class="gp">... </span>    <span class="n">PAR</span><span class="p">(</span><span class="s">"And then ..."</span><span class="p">)</span>
 932 <span class="gp">... </span>  <span class="p">),</span>
 933 <span class="gp">... </span>  <span class="n">SECTION</span><span class="p">(</span>
 934 <span class="gp">... </span>    <span class="n">TITLE</span><span class="p">(</span><span class="s">"The hog"</span><span class="p">),</span>
 935 <span class="gp">... </span>    <span class="n">PAR</span><span class="p">(</span><span class="s">"Sooner or later ..."</span><span class="p">)</span>
 936 <span class="gp">... </span>  <span class="p">)</span>
 937 <span class="gp">... </span><span class="p">)</span>
 938
 939 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">etree</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">my_doc</span><span class="p">,</span> <span class="n">pretty_print</span><span class="o">=</span><span class="bp">True</span><span class="p">))</span>
 940 <span class="go">&lt;p:doc xmlns:p="http://my.de/fault/namespace"&gt;</span>
 941 <span class="go">  &lt;p:title&gt;The dog and the hog&lt;/p:title&gt;</span>
 942 <span class="go">  &lt;p:section&gt;</span>
 943 <span class="go">    &lt;p:title&gt;The dog&lt;/p:title&gt;</span>
 944 <span class="go">    &lt;p:par&gt;Once upon a time, ...&lt;/p:par&gt;</span>
 945 <span class="go">    &lt;p:par&gt;And then ...&lt;/p:par&gt;</span>
 946 <span class="go">  &lt;/p:section&gt;</span>
 947 <span class="go">  &lt;p:section&gt;</span>
 948 <span class="go">    &lt;p:title&gt;The hog&lt;/p:title&gt;</span>
 949 <span class="go">    &lt;p:par&gt;Sooner or later ...&lt;/p:par&gt;</span>
 950 <span class="go">  &lt;/p:section&gt;</span>
 951 <span class="go">&lt;/p:doc&gt;</span>
 952 </pre></div>
 953 <p>One such example is the module <tt class="docutils literal">lxml.html.builder</tt>, which provides a
 954 vocabulary for HTML.</p>
 955 <p>When dealing with multiple namespaces, it is good practice to define
 956 one ElementMaker for each namespace URI.  Again, note how the above
 957 example predefines the tag builders in named constants.  That makes it
 958 easy to put all tag declarations of a namespace into one Python module
 959 and to import/use the tag name constants from there.  This avoids
 960 pitfalls like typos or accidentally missing namespaces.</p>
 961 </div>
 962 <div class="section" id="elementpath">
 963 <h1>ElementPath</h1>
 964 <p>The ElementTree library comes with a simple XPath-like path language
 965 called <a class="reference external" href="http://effbot.org/zone/element-xpath.htm">ElementPath</a>.  The main difference is that you can use the
 966 <tt class="docutils literal">{namespace}tag</tt> notation in ElementPath expressions.  However,
 967 advanced features like value comparison and functions are not
 968 available.</p>
 969 <p>In addition to a <a class="reference external" href="xpathxslt.html#xpath">full XPath implementation</a>, lxml.etree supports the
 970 ElementPath language in the same way ElementTree does, even using
 971 (almost) the same implementation.  The API provides four methods here
 972 that you can find on Elements and ElementTrees:</p>
 973 <ul class="simple">
 974 <li><tt class="docutils literal">iterfind()</tt> iterates over all Elements that match the path
 975 expression</li>
 976 <li><tt class="docutils literal">findall()</tt> returns a list of matching Elements</li>
 977 <li><tt class="docutils literal">find()</tt> efficiently returns only the first match</li>
 978 <li><tt class="docutils literal">findtext()</tt> returns the <tt class="docutils literal">.text</tt> content of the first match</li>
 979 </ul>
 980 <p>Here are some examples:</p>
 981 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">root</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">"&lt;root&gt;&lt;a x='123'&gt;aText&lt;b/&gt;&lt;c/&gt;&lt;b/&gt;&lt;/a&gt;&lt;/root&gt;"</span><span class="p">)</span>
 982 </pre></div>
 983 <p>Find a child of an Element:</p>
 984 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="s">"b"</span><span class="p">))</span>
 985 <span class="go">None</span>
 986 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="s">"a"</span><span class="p">)</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 987 <span class="go">a</span>
 988 </pre></div>
 989 <p>Find an Element anywhere in the tree:</p>
 990 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="s">".//b"</span><span class="p">)</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 991 <span class="go">b</span>
 992 <span class="gp">&gt;&gt;&gt; </span><span class="p">[</span> <span class="n">b</span><span class="o">.</span><span class="n">tag</span> <span class="k">for</span> <span class="n">b</span> <span class="ow">in</span> <span class="n">root</span><span class="o">.</span><span class="n">iterfind</span><span class="p">(</span><span class="s">".//b"</span><span class="p">)</span> <span class="p">]</span>
 993 <span class="go">['b', 'b']</span>
 994 </pre></div>
 995 <p>Find Elements with a certain attribute:</p>
 996 <div class="syntax"><pre><span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">findall</span><span class="p">(</span><span class="s">".//a[@x]"</span><span class="p">)[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">tag</span><span class="p">)</span>
 997 <span class="go">a</span>
 998 <span class="gp">&gt;&gt;&gt; </span><span class="k">print</span><span class="p">(</span><span class="n">root</span><span class="o">.</span><span class="n">findall</span><span class="p">(</span><span class="s">".//a[@y]"</span><span class="p">))</span>
 999 <span class="go">[]</span>
1000 </pre></div>
1001 </div>
1002 </div>
1003 <div class="footer">
1004 <hr class="footer" />
1005 Generated on: 2012-07-31.
1006
1007 </div>
1008 </body>
1009 </html>