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POWhy doesn't xpath work when processing an XHTML document with lxml (in python)?
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  1. POWhy doesn't xpath work when processing an XHTML document with lxml (in python)?
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    copied!<p>I am testing against the following test document:</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"&gt; &lt;html xmlns="http://www.w3.org/1999/xhtml"&gt; &lt;head&gt; &lt;title&gt;hi there&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;img class="foo" src="bar.png"/&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>If I parse the document using lxml.html, I can get the IMG with an xpath just fine:</p> <pre><code>&gt;&gt;&gt; root = lxml.html.fromstring(doc) &gt;&gt;&gt; root.xpath("//img") [&lt;Element img at 1879e30&gt;] </code></pre> <p>However, if I parse the document as XML and try to get the IMG tag, I get an empty result:</p> <pre><code>&gt;&gt;&gt; tree = etree.parse(StringIO(doc)) &gt;&gt;&gt; tree.getroot().xpath("//img") [] </code></pre> <p>I can navigate to the element directly:</p> <pre><code>&gt;&gt;&gt; tree.getroot().getchildren()[1].getchildren()[0] &lt;Element {http://www.w3.org/1999/xhtml}img at f56810&gt; </code></pre> <p>But of course that doesn't help me process arbitrary documents. I would also expect to be able to query etree to get an xpath expression that will directly identify this element, which, technically I can do:</p> <pre><code>&gt;&gt;&gt; tree.getpath(tree.getroot().getchildren()[1].getchildren()[0]) '/*/*[2]/*' &gt;&gt;&gt; tree.getroot().xpath('/*/*[2]/*') [&lt;Element {http://www.w3.org/1999/xhtml}img at fa1750&gt;] </code></pre> <p>But that xpath is, again, obviously not useful for parsing arbitrary documents.</p> <p>Obviously I am missing some key issue here, but I don't know what it is. My best guess is that it has something to do with namespaces but the only namespace defined is the default and I don't know what else I might need to consider in regards to namespaces.</p> <p>So, what am I missing?</p>
 

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