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class="menu item"><a href="lxml-source-howto.html#where-to-start">Where to start?</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-etree">lxml.etree</a></li><li class="menu item"><a href="lxml-source-howto.html#python-modules">Python modules</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-objectify">lxml.objectify</a></li><li class="menu item"><a href="lxml-source-howto.html#lxml-html">lxml.html</a></li></ul></li></ul><ul class="menu foreign" id="changes 4 2 1-menu"><li class="menu title"><a href="changes-4.2.1.html">Release Changelog</a></li></ul><ul class="menu foreign" id="credits-menu"><li class="menu title"><a href="credits.html">Credits</a><ul class="submenu"><li class="menu item"><a href="credits.html#main-contributors">Main contributors</a></li><li class="menu item"><a href="credits.html#special-thanks-goes-to">Special thanks goes to:</a></li></ul></li></ul></li><li><a href="http://lxml.de/sitemap.html">Sitemap</a></li></ul></div></div><h1 class="title">BeautifulSoup Parser</h1>
<p><a class="reference external" href="http://www.crummy.com/software/BeautifulSoup/">BeautifulSoup</a> is a Python package for working with real-world and broken HTML,
just like <a class="reference external" href="lxmlhtml.html">lxml.html</a>. As of version 4.x, it can use
<a class="reference external" href="http://www.crummy.com/software/BeautifulSoup/bs4/doc/#installing-a-parser">different HTML parsers</a>,
each of which has its advantages and disadvantages (see the link).</p>
<p>lxml can make use of BeautifulSoup as a parser backend, just like BeautifulSoup
can employ lxml as a parser. When using BeautifulSoup from lxml, however, the
default is to use Python's integrated HTML parser in the
<a class="reference external" href="https://docs.python.org/3/library/html.parser.html">html.parser</a> module.
In order to make use of the HTML5 parser of
<a class="reference external" href="https://pypi.python.org/pypi/html5lib">html5lib</a> instead, it is better
to go directly through the <a class="reference external" href="html5parser.html">html5parser module</a> in
<tt class="docutils literal">lxml.html</tt>.</p>
<p>A very nice feature of BeautifulSoup is its excellent <a class="reference external" href="http://www.crummy.com/software/BeautifulSoup/bs4/doc/#unicode-dammit">support for encoding
detection</a> which can provide better results for real-world HTML pages that
do not (correctly) declare their encoding.</p>
<p>lxml interfaces with BeautifulSoup through the <tt class="docutils literal">lxml.html.soupparser</tt>
module. It provides three main functions: <tt class="docutils literal">fromstring()</tt> and <tt class="docutils literal">parse()</tt>
to parse a string or file using BeautifulSoup into an <tt class="docutils literal">lxml.html</tt>
document, and <tt class="docutils literal">convert_tree()</tt> to convert an existing BeautifulSoup
tree into a list of top-level Elements.</p>
<div class="contents topic" id="contents">
<p class="topic-title first">Contents</p>
<ul class="simple">
<li><a class="reference internal" href="#parsing-with-the-soupparser" id="id1">Parsing with the soupparser</a></li>
<li><a class="reference internal" href="#entity-handling" id="id2">Entity handling</a></li>
<li><a class="reference internal" href="#using-soupparser-as-a-fallback" id="id3">Using soupparser as a fallback</a></li>
<li><a class="reference internal" href="#using-only-the-encoding-detection" id="id4">Using only the encoding detection</a></li>
</ul>
</div>
<div class="section" id="parsing-with-the-soupparser">
<h1>Parsing with the soupparser</h1>
<p>The functions <tt class="docutils literal">fromstring()</tt> and <tt class="docutils literal">parse()</tt> behave as known from
lxml. The first returns a root Element, the latter returns an
ElementTree.</p>
<p>There is also a legacy module called <tt class="docutils literal">lxml.html.ElementSoup</tt>, which
mimics the interface provided by Fredrik Lundh's <a class="reference external" href="http://effbot.org/zone/element-soup.htm">ElementSoup</a>
module. Note that the <tt class="docutils literal">soupparser</tt> module was added in lxml 2.0.3.
Previous versions of lxml 2.0.x only have the <tt class="docutils literal">ElementSoup</tt> module.</p>
<p>Here is a document full of tag soup, similar to, but not quite like, HTML:</p>
<div class="syntax"><pre><span class="gp">>>> </span><span class="n">tag_soup</span> <span class="o">=</span> <span class="s1">'''</span>
<span class="gp">... </span><span class="s1"><meta/><head><title>Hello</head><body onload=crash()>Hi all<p>'''</span>
</pre></div>
<p>All you need to do is pass it to the <tt class="docutils literal">fromstring()</tt> function:</p>
<div class="syntax"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">lxml.html.soupparser</span> <span class="kn">import</span> <span class="n">fromstring</span>
<span class="gp">>>> </span><span class="n">root</span> <span class="o">=</span> <span class="n">fromstring</span><span class="p">(</span><span class="n">tag_soup</span><span class="p">)</span>
</pre></div>
<p>To see what we have here, you can serialise it:</p>
<div class="syntax"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">lxml.etree</span> <span class="kn">import</span> <span class="n">tostring</span>
<span class="gp">>>> </span><span class="k">print</span><span class="p">(</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><span class="o">.</span><span class="n">strip</span><span class="p">())</span>
<span class="go"><html></span>
<span class="go"> <meta/></span>
<span class="go"> <head></span>
<span class="go"> <title>Hello</title></span>
<span class="go"> </head></span>
<span class="go"> <body onload="crash()">Hi all<p/></body></span>
<span class="go"></html></span>
</pre></div>
<p>Not quite what you'd expect from an HTML page, but, well, it was broken
already, right? The parser did its best, and so now it's a tree.</p>
<p>To control how Element objects are created during the conversion
of the tree, you can pass a <tt class="docutils literal">makeelement</tt> factory function to
<tt class="docutils literal">parse()</tt> and <tt class="docutils literal">fromstring()</tt>. By default, this is based on the
HTML parser defined in <tt class="docutils literal">lxml.html</tt>.</p>
<p>For a quick comparison, libxml2 2.9.1 parses the same tag soup as
follows. The only difference is that libxml2 tries harder to adhere
to the structure of an HTML document and moves misplaced tags where
they (likely) belong. Note, however, that the result can vary between
parser versions.</p>
<div class="syntax"><pre><span class="p"><</span><span class="nt">html</span><span class="p">></span>
<span class="p"><</span><span class="nt">head</span><span class="p">></span>
<span class="p"><</span><span class="nt">meta</span><span class="p">/></span>
<span class="p"><</span><span class="nt">title</span><span class="p">></span>Hello<span class="p"></</span><span class="nt">title</span><span class="p">></span>
<span class="p"></</span><span class="nt">head</span><span class="p">></span>
<span class="p"><</span><span class="nt">body</span> <span class="na">onload</span><span class="o">=</span><span class="s">"crash()"</span><span class="p">></span>Hi all<span class="p"><</span><span class="nt">p</span><span class="p">/></</span><span class="nt">body</span><span class="p">></span>
<span class="p"></</span><span class="nt">html</span><span class="p">></span>
</pre></div>
</div>
<div class="section" id="entity-handling">
<h1>Entity handling</h1>
<p>By default, the BeautifulSoup parser also replaces the entities it
finds by their character equivalent.</p>
<div class="syntax"><pre><span class="gp">>>> </span><span class="n">tag_soup</span> <span class="o">=</span> <span class="s1">'<body>&copy;&euro;&#45;&#245;&#445;<p>'</span>
<span class="gp">>>> </span><span class="n">body</span> <span class="o">=</span> <span class="n">fromstring</span><span class="p">(</span><span class="n">tag_soup</span><span class="p">)</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="s1">'.//body'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">body</span><span class="o">.</span><span class="n">text</span>
<span class="go">u'\xa9\u20ac-\xf5\u01bd'</span>
</pre></div>
<p>If you want them back on the way out, you can just serialise with the
default encoding, which is 'US-ASCII'.</p>
<div class="syntax"><pre><span class="gp">>>> </span><span class="n">tostring</span><span class="p">(</span><span class="n">body</span><span class="p">)</span>
<span class="go">'<body>&#169;&#8364;-&#245;&#445;<p/></body>'</span>
<span class="gp">>>> </span><span class="n">tostring</span><span class="p">(</span><span class="n">body</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s2">"html"</span><span class="p">)</span>
<span class="go">'<body>&#169;&#8364;-&#245;&#445;<p></p></body>'</span>
</pre></div>
<p>Any other encoding will output the respective byte sequences.</p>
<div class="syntax"><pre><span class="gp">>>> </span><span class="n">tostring</span><span class="p">(</span><span class="n">body</span><span class="p">,</span> <span class="n">encoding</span><span class="o">=</span><span class="s2">"utf-8"</span><span class="p">)</span>
<span class="go">'<body>\xc2\xa9\xe2\x82\xac-\xc3\xb5\xc6\xbd<p/></body>'</span>
<span class="gp">>>> </span><span class="n">tostring</span><span class="p">(</span><span class="n">body</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s2">"html"</span><span class="p">,</span> <span class="n">encoding</span><span class="o">=</span><span class="s2">"utf-8"</span><span class="p">)</span>
<span class="go">'<body>\xc2\xa9\xe2\x82\xac-\xc3\xb5\xc6\xbd<p></p></body>'</span>
<span class="gp">>>> </span><span class="n">tostring</span><span class="p">(</span><span class="n">body</span><span class="p">,</span> <span class="n">encoding</span><span class="o">=</span><span class="s1">'unicode'</span><span class="p">)</span>
<span class="go">u'<body>\xa9\u20ac-\xf5\u01bd<p/></body>'</span>
<span class="gp">>>> </span><span class="n">tostring</span><span class="p">(</span><span class="n">body</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s2">"html"</span><span class="p">,</span> <span class="n">encoding</span><span class="o">=</span><span class="s1">'unicode'</span><span class="p">)</span>
<span class="go">u'<body>\xa9\u20ac-\xf5\u01bd<p></p></body>'</span>
</pre></div>
</div>
<div class="section" id="using-soupparser-as-a-fallback">
<h1>Using soupparser as a fallback</h1>
<p>The downside of using this parser is that it is <a class="reference external" href="http://blog.ianbicking.org/2008/03/30/python-html-parser-performance/">much slower</a> than
the C implemented HTML parser of libxml2 that lxml uses. So if
performance matters, you might want to consider using <tt class="docutils literal">soupparser</tt>
only as a fallback for certain cases.</p>
<p>One common problem of lxml's parser is that it might not get the
encoding right in cases where the document contains a <tt class="docutils literal"><meta></tt> tag
at the wrong place. In this case, you can exploit the fact that lxml
serialises much faster than most other HTML libraries for Python.
Just serialise the document to unicode and if that gives you an
exception, re-parse it with BeautifulSoup to see if that works
better.</p>
<div class="syntax"><pre><span class="gp">>>> </span><span class="n">tag_soup</span> <span class="o">=</span> <span class="s1">'''</span><span class="se">\</span>
<span class="gp">... </span><span class="s1"><meta http-equiv="Content-Type"</span>
<span class="gp">... </span><span class="s1"> content="text/html;charset=utf-8" /></span>
<span class="gp">... </span><span class="s1"><html></span>
<span class="gp">... </span><span class="s1"> <head></span>
<span class="gp">... </span><span class="s1"> <title>Hello W</span><span class="se">\xc3\xb6</span><span class="s1">rld!</title></span>
<span class="gp">... </span><span class="s1"> </head></span>
<span class="gp">... </span><span class="s1"> <body>Hi all</body></span>
<span class="gp">... </span><span class="s1"></html>'''</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">lxml.html</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">lxml.html.soupparser</span>
<span class="gp">>>> </span><span class="n">root</span> <span class="o">=</span> <span class="n">lxml</span><span class="o">.</span><span class="n">html</span><span class="o">.</span><span class="n">fromstring</span><span class="p">(</span><span class="n">tag_soup</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">try</span><span class="p">:</span>
<span class="gp">... </span> <span class="n">ignore</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="s1">'unicode'</span><span class="p">)</span>
<span class="gp">... </span><span class="k">except</span> <span class="ne">UnicodeDecodeError</span><span class="p">:</span>
<span class="gp">... </span> <span class="n">root</span> <span class="o">=</span> <span class="n">lxml</span><span class="o">.</span><span class="n">html</span><span class="o">.</span><span class="n">soupparser</span><span class="o">.</span><span class="n">fromstring</span><span class="p">(</span><span class="n">tag_soup</span><span class="p">)</span>
</pre></div>
</div>
<div class="section" id="using-only-the-encoding-detection">
<h1>Using only the encoding detection</h1>
<p>Even if you prefer lxml's fast HTML parser, you can still benefit
from BeautifulSoup's <a class="reference external" href="http://www.crummy.com/software/BeautifulSoup/bs4/doc/#unicode-dammit">support for encoding detection</a> in the
<tt class="docutils literal">UnicodeDammit</tt> class. Once it succeeds in decoding the data,
you can simply pass the resulting Unicode string into lxml's parser.</p>
<div class="syntax"><pre><span class="gp">>>> </span><span class="k">try</span><span class="p">:</span>
<span class="gp">... </span> <span class="kn">from</span> <span class="nn">bs4</span> <span class="kn">import</span> <span class="n">UnicodeDammit</span> <span class="c1"># BeautifulSoup 4</span>
<span class="gp">...</span>
<span class="gp">... </span> <span class="k">def</span> <span class="nf">decode_html</span><span class="p">(</span><span class="n">html_string</span><span class="p">):</span>
<span class="gp">... </span> <span class="n">converted</span> <span class="o">=</span> <span class="n">UnicodeDammit</span><span class="p">(</span><span class="n">html_string</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">if</span> <span class="ow">not</span> <span class="n">converted</span><span class="o">.</span><span class="n">unicode_markup</span><span class="p">:</span>
<span class="gp">... </span> <span class="k">raise</span> <span class="ne">UnicodeDecodeError</span><span class="p">(</span>
<span class="gp">... </span> <span class="s2">"Failed to detect encoding, tried [</span><span class="si">%s</span><span class="s2">]"</span><span class="p">,</span>
<span class="gp">... </span> <span class="s1">', '</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">converted</span><span class="o">.</span><span class="n">tried_encodings</span><span class="p">))</span>
<span class="gp">... </span> <span class="c1"># print converted.original_encoding</span>
<span class="gp">... </span> <span class="k">return</span> <span class="n">converted</span><span class="o">.</span><span class="n">unicode_markup</span>
<span class="gp">...</span>
<span class="gp">... </span><span class="k">except</span> <span class="ne">ImportError</span><span class="p">:</span>
<span class="gp">... </span> <span class="kn">from</span> <span class="nn">BeautifulSoup</span> <span class="kn">import</span> <span class="n">UnicodeDammit</span> <span class="c1"># BeautifulSoup 3</span>
<span class="gp">...</span>
<span class="gp">... </span> <span class="k">def</span> <span class="nf">decode_html</span><span class="p">(</span><span class="n">html_string</span><span class="p">):</span>
<span class="gp">... </span> <span class="n">converted</span> <span class="o">=</span> <span class="n">UnicodeDammit</span><span class="p">(</span><span class="n">html_string</span><span class="p">,</span> <span class="n">isHTML</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">if</span> <span class="ow">not</span> <span class="n">converted</span><span class="o">.</span><span class="n">unicode</span><span class="p">:</span>
<span class="gp">... </span> <span class="k">raise</span> <span class="ne">UnicodeDecodeError</span><span class="p">(</span>
<span class="gp">... </span> <span class="s2">"Failed to detect encoding, tried [</span><span class="si">%s</span><span class="s2">]"</span><span class="p">,</span>
<span class="gp">... </span> <span class="s1">', '</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">converted</span><span class="o">.</span><span class="n">triedEncodings</span><span class="p">))</span>
<span class="gp">... </span> <span class="c1"># print converted.originalEncoding</span>
<span class="gp">... </span> <span class="k">return</span> <span class="n">converted</span><span class="o">.</span><span class="n">unicode</span>
<span class="gp">>>> </span><span class="n">root</span> <span class="o">=</span> <span class="n">lxml</span><span class="o">.</span><span class="n">html</span><span class="o">.</span><span class="n">fromstring</span><span class="p">(</span><span class="n">decode_html</span><span class="p">(</span><span class="n">tag_soup</span><span class="p">))</span>
</pre></div>
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