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class="submenu"><li class="menu item"><a href="credits.html#main-contributors">Main contributors</a></li><li class="menu item"><a href="credits.html#special-thanks-goes-to">Special thanks goes to:</a></li></ul></li></ul></li><li><a href="http://lxml.de/sitemap.html">Sitemap</a></li></ul></div><h1 class="title">lxml.cssselect</h1>

lxml supports a number of interesting languages for tree traversal and element
selection. The most important is obviously <a class="reference external" href="xpathxslt.html#xpath">XPath</a>, but there is also
<a class="reference external" href="objectify.html#objectpath">ObjectPath</a> in the <a class="reference external" href="objectify.html">lxml.objectify</a> module. The newest child of this family
is <a class="reference external" href="http://www.w3.org/TR/CSS21/selector.html">CSS selection</a>, which is made available in form of the <tt class="docutils literal">lxml.cssselect</tt>
module.
Although it started its life in lxml, <a class="reference external" href="http://packages.python.org/cssselect/">cssselect</a> is now an independent project.
It translates CSS selectors to XPath 1.0 expressions that can be used with
lxml's XPath engine. <tt class="docutils literal">lxml.cssselect</tt> adds a few convenience shortcuts into
that package.
<div class="contents topic" id="contents">
Contents
<ul class="simple">
<li><a class="reference internal" href="#the-cssselector-class" id="id1">The CSSSelector class</a></li>
<li><a class="reference internal" href="#the-cssselect-method" id="id2">The cssselect method</a></li>
<li><a class="reference internal" href="#supported-selectors" id="id3">Supported Selectors</a></li>
<li><a class="reference internal" href="#namespaces" id="id4">Namespaces</a></li>
</ul>
</div>
<div class="section" id="the-cssselector-class">
<h1>The CSSSelector class</h1>
The most important class in the <tt class="docutils literal">lxml.cssselect</tt> module is <tt class="docutils literal">CSSSelector</tt>. It
provides the same interface as the <a class="reference external" href="xpathxslt.html#xpath">XPath</a> class, but accepts a CSS selector
expression as input:
<div class="syntax"><pre>&gt;&gt;&gt; from lxml.cssselect import CSSSelector
&gt;&gt;&gt; sel = CSSSelector('div.content')
&gt;&gt;&gt; sel #doctest: +ELLIPSIS
&lt;CSSSelector ... for 'div.content'&gt;
&gt;&gt;&gt; sel.css
'div.content'
</pre></div>
The selector actually compiles to XPath, and you can see the
expression by inspecting the object:
<div class="syntax"><pre>&gt;&gt;&gt; sel.path
"descendant-or-self::div[@class and contains(concat(' ', normalize-space(@class), ' '), ' content ')]"
</pre></div>
To use the selector, simply call it with a document or element
object:
<div class="syntax"><pre>&gt;&gt;&gt; from lxml.etree import fromstring
&gt;&gt;&gt; h = fromstring('''&lt;div id="outer"&gt;
... &lt;div id="inner" class="content body"&gt;
... text
... &lt;/div&gt;&lt;/div&gt;''')
&gt;&gt;&gt; [e.get('id') for e in sel(h)]
['inner']
</pre></div>
Using <tt class="docutils literal">CSSSelector</tt> is equivalent to translating with <tt class="docutils literal">cssselect</tt>
and using the <tt class="docutils literal">XPath</tt> class:
<div class="syntax"><pre>&gt;&gt;&gt; from cssselect import GenericTranslator
&gt;&gt;&gt; from lxml.etree import XPath
&gt;&gt;&gt; sel = XPath(GenericTranslator().css_to_xpath('div.content'))
</pre></div>
<tt class="docutils literal">CSSSelector</tt> takes a <tt class="docutils literal">translator</tt> parameter to let you choose which
translator to use. It can be <tt class="docutils literal">'xml'</tt> (the default), <tt class="docutils literal">'xhtml'</tt>, <tt class="docutils literal">'html'</tt>
or a <a class="reference external" href="http://packages.python.org/cssselect/#cssselect.GenericTranslator">Translator object</a>.
</div>
<div class="section" id="the-cssselect-method">
<h1>The cssselect method</h1>
lxml <tt class="docutils literal">Element</tt> objects have a <tt class="docutils literal">cssselect</tt> convenience method.
<div class="syntax"><pre>&gt;&gt;&gt; h.cssselect('div.content') == sel(h)
True
</pre></div>
Note however that pre-compiling the expression with the <tt class="docutils literal">CSSSelector</tt> or
<tt class="docutils literal">XPath</tt> class can provide a substantial speedup.
The method also accepts a <tt class="docutils literal">translator</tt> parameter. On <tt class="docutils literal">HtmlElement</tt>
objects, the default is changed to <tt class="docutils literal">'html'</tt>.
</div>
<div class="section" id="supported-selectors">
<h1>Supported Selectors</h1>
Most <a class="reference external" href="http://www.w3.org/TR/2011/REC-css3-selectors-20110929/">Level 3</a> selectors are supported. The details are in the
<a class="reference external" href="http://packages.python.org/cssselect/#supported-selectors">cssselect documentation</a>.
</div>
<div class="section" id="namespaces">
<h1>Namespaces</h1>
In CSS you can use <tt class="docutils literal">namespace-prefix|element</tt>, similar to
<tt class="docutils literal">namespace-prefix:element</tt> in an XPath expression. In fact, it maps
one-to-one, and the same rules are used to map namespace prefixes to
namespace URIs: the <tt class="docutils literal">CSSSelector</tt> class accepts a dictionary as its
<tt class="docutils literal">namespaces</tt> argument.
</div>
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