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//usr/share/doc/python-lxml-2.0.11/doc/html/cssselect.html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="generator" content="Docutils 0.4.1: http://docutils.sourceforge.net/" /> <title>lxml.cssselect</title> <link rel="stylesheet" href="style.css" type="text/css" /> </head> <body> <div class="document" id="lxml-cssselect"> <div class="sidemenu"><ul id="lxml"><li><span class="section title">lxml</span><ul class="menu foreign" id="index"><li class="menu title"><a href="index.html">lxml</a><ul class="submenu"><li class="menu item"><a href="index.html#introduction">Introduction</a></li><li class="menu item"><a href="index.html#documentation">Documentation</a></li><li class="menu item"><a href="index.html#download">Download</a></li><li class="menu item"><a href="index.html#mailing-list">Mailing list</a></li><li 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Diff</a></li><li class="menu item"><a href="lxmlhtml.html#examples">Examples</a></li></ul></li></ul><ul class="menu current" id="cssselect"><li class="menu title"><a href="cssselect.html">lxml.cssselect</a><ul class="submenu"><li class="menu item"><a href="cssselect.html#the-cssselector-class">The CSSSelector class</a></li><li class="menu item"><a href="cssselect.html#css-selectors">CSS Selectors</a></li><li class="menu item"><a href="cssselect.html#limitations">Limitations</a></li></ul></li></ul><ul class="menu foreign" id="elementsoup"><li class="menu title"><a href="elementsoup.html">BeautifulSoup Parser</a><ul class="submenu"><li class="menu item"><a href="elementsoup.html#entity-handling">Entity handling</a></li><li class="menu item"><a href="elementsoup.html#using-soupparser-as-a-fallback">Using soupparser as a fallback</a></li></ul></li></ul></li></ul><ul id="Extending lxml"><li><span class="section title">Extending lxml</span><ul class="menu foreign" id="resolvers"><li 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class="menu item"><a href="build.html#setuptools">Setuptools</a></li><li class="menu item"><a href="build.html#running-the-tests-and-reporting-errors">Running the tests and reporting errors</a></li><li class="menu item"><a href="build.html#contributing-an-egg">Contributing an egg</a></li><li class="menu item"><a href="build.html#providing-newer-library-versions-on-mac-os-x">Providing newer library versions on Mac-OS X</a></li><li class="menu item"><a href="build.html#static-linking-on-windows">Static linking on Windows</a></li><li class="menu item"><a href="build.html#building-debian-packages-from-svn-sources">Building Debian packages from SVN sources</a></li></ul></li></ul><ul class="menu foreign" id="lxml source howto"><li class="menu title"><a href="lxml-source-howto.html">How to read the source of lxml</a><ul class="submenu"><li class="menu item"><a href="lxml-source-howto.html#what-is-cython?">What is Cython?</a></li><li class="menu item"><a href="lxml-source-howto.html#where-to-start?">Where to start?</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-etree">lxml.etree</a></li><li class="menu item"><a href="lxml-source-howto.html#python-modules">Python modules</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-objectify">lxml.objectify</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-pyclasslookup">lxml.pyclasslookup</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-html">lxml.html</a></li></ul></li></ul><ul class="menu foreign" id="changes 2 0 11"><li class="menu title"><a href="changes-2.0.11.html">Release Changelog</a></li></ul><ul class="menu foreign" id="credits"><li class="menu title"><a href="credits.html">Credits</a><ul class="submenu"><li class="menu item"><a href="credits.html#special-thanks-goes-to:">Special thanks goes to:</a></li></ul></li></ul></li></ul></div><h1 class="title">lxml.cssselect</h1> <p>lxml supports a number of interesting languages for tree traversal and element selection. The most important is obviously <a class="reference" href="xpathxslt.html#xpath">XPath</a>, but there is also <a class="reference" href="objectify.html#objectpath">ObjectPath</a> in the <a class="reference" href="objectify.html">lxml.objectify</a> module. The newest child of this family is <a class="reference" href="http://www.w3.org/TR/CSS21/selector.html">CSS selection</a>, which is implemented in the new <tt class="docutils literal"><span class="pre">lxml.cssselect</span></tt> module.</p> <div class="contents topic"> <p class="topic-title first"><a id="contents" name="contents">Contents</a></p> <ul class="simple"> <li><a class="reference" href="#the-cssselector-class" id="id1" name="id1">The CSSSelector class</a></li> <li><a class="reference" href="#css-selectors" id="id2" name="id2">CSS Selectors</a><ul> <li><a class="reference" href="#namespaces" id="id3" name="id3">Namespaces</a></li> </ul> </li> <li><a class="reference" href="#limitations" id="id4" name="id4">Limitations</a></li> </ul> </div> <div class="section"> <h1><a id="the-cssselector-class" name="the-cssselector-class">The CSSSelector class</a></h1> <p>The most important class in the <tt class="docutils literal"><span class="pre">cssselect</span></tt> module is <tt class="docutils literal"><span class="pre">CSSSelector</span></tt>. It provides the same interface as the <a class="reference" href="xpathxslt.html#xpath">XPath</a> class, but accepts a CSS selector expression as input:</p> <pre class="literal-block"> >>> from lxml.cssselect import CSSSelector >>> sel = CSSSelector('div.content') >>> sel #doctest: +ELLIPSIS <CSSSelector ... for 'div.content'> >>> sel.css 'div.content' </pre> <p>The selector actually compiles to XPath, and you can see the expression by inspecting the object:</p> <pre class="literal-block"> >>> sel.path "descendant-or-self::div[contains(concat(' ', normalize-space(@class), ' '), ' content ')]" </pre> <p>To use the selector, simply call it with a document or element object:</p> <pre class="literal-block"> >>> from lxml.etree import fromstring >>> h = fromstring('''<div id="outer"> ... <div id="inner" class="content body"> ... text ... </div></div>''') >>> [e.get('id') for e in sel(h)] ['inner'] </pre> </div> <div class="section"> <h1><a id="css-selectors" name="css-selectors">CSS Selectors</a></h1> <p>This libraries attempts to implement CSS selectors <a class="reference" href="http://www.w3.org/TR/2001/CR-css3-selectors-20011113/">as described in the w3c specification</a>. Many of the pseudo-classes do not apply in this context, including all <a class="reference" href="http://www.w3.org/TR/2001/CR-css3-selectors-20011113/#dynamic-pseudos">dynamic pseudo-classes</a>. In particular these will not be available:</p> <ul class="simple"> <li>link state: <tt class="docutils literal"><span class="pre">:link</span></tt>, <tt class="docutils literal"><span class="pre">:visited</span></tt>, <tt class="docutils literal"><span class="pre">:target</span></tt></li> <li>actions: <tt class="docutils literal"><span class="pre">:hover</span></tt>, <tt class="docutils literal"><span class="pre">:active</span></tt>, <tt class="docutils literal"><span class="pre">:focus</span></tt></li> <li>UI states: <tt class="docutils literal"><span class="pre">:enabled</span></tt>, <tt class="docutils literal"><span class="pre">:disabled</span></tt>, <tt class="docutils literal"><span class="pre">:indeterminate</span></tt> (<tt class="docutils literal"><span class="pre">:checked</span></tt> and <tt class="docutils literal"><span class="pre">:unchecked</span></tt> <em>are</em> available)</li> </ul> <p>Also, none of the psuedo-elements apply, because the selector only returns elements and psuedo-elements select portions of text, like <tt class="docutils literal"><span class="pre">::first-line</span></tt>.</p> <div class="section"> <h2><a id="namespaces" name="namespaces">Namespaces</a></h2> <p>In CSS you can use <tt class="docutils literal"><span class="pre">namespace-prefix|element</span></tt>, similar to <tt class="docutils literal"><span class="pre">namespace-prefix:element</span></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.</p> </div> </div> <div class="section"> <h1><a id="limitations" name="limitations">Limitations</a></h1> <p>These applicable pseudoclasses are not yet implemented:</p> <ul class="simple"> <li><tt class="docutils literal"><span class="pre">:lang(language)</span></tt></li> <li><tt class="docutils literal"><span class="pre">:root</span></tt></li> <li><tt class="docutils literal"><span class="pre">*:first-of-type</span></tt>, <tt class="docutils literal"><span class="pre">*:last-of-type</span></tt>, <tt class="docutils literal"><span class="pre">*:nth-of-type</span></tt>, <tt class="docutils literal"><span class="pre">*:nth-last-of-type</span></tt>, <tt class="docutils literal"><span class="pre">*:only-of-type</span></tt>. All of these work when you specify an element type, but not with <tt class="docutils literal"><span class="pre">*</span></tt></li> </ul> <p>Unlike XPath you cannot provide parameters in your expressions -- all expressions are completely static.</p> <p>XPath has underspecified string quoting rules (there seems to be no string quoting at all), so if you use expressions that contain characters that requiring quoting you might have problems with the translation from CSS to XPath.</p> </div> </div> <div class="footer"> <hr class="footer" /> Generated on: 2008-12-12. </div> </body> </html>