Using lxml to parse namepaced HTML?

This is driving me totally nuts, I've been struggling with it for many hours. Any help would be much appreciated.

I'm using PyQuery 1.2.9 (which is built on top of lxml) to scrape this URL. I just want to get a list of all the links in the .linkoutlist section.

This is my request in full:

response = requests.get('http://www.ncbi.nlm.nih.gov/pubmed/?term=The%20cost-effectiveness%20of%20mirtazapine%20versus%20paroxetine%20in%20treating%20people%20with%20depression%20in%20primary%20care')
doc = pq(response.content)
links = doc('#maincontent .linkoutlist a')
print links

But that returns an empty array. If I use this query instead:

links = doc('#maincontent .linkoutlist')

Then I get this back this HTML:

<div xmlns="http://www.w3.org/1999/xhtml" xmlns:xi="http://www.w3.org/2001/XInclude" class="linkoutlist">
   <h4>Full Text Sources</h4>
   <ul>
      <li><a title="Full text at publisher's site" href="http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=0268-1315&amp;volume=19&amp;issue=3&amp;spage=125" ref="itool=Abstract&amp;PrId=3159&amp;uid=15107654&amp;db=pubmed&amp;log$=linkoutlink&amp;nlmid=8609061" target="_blank">Lippincott Williams &amp; Wilkins</a></li>
      <li><a href="http://ovidsp.ovid.com/ovidweb.cgi?T=JS&amp;PAGE=linkout&amp;SEARCH=15107654.ui" ref="itool=Abstract&amp;PrId=3682&amp;uid=15107654&amp;db=pubmed&amp;log$=linkoutlink&amp;nlmid=8609061" target="_blank">Ovid Technologies, Inc.</a></li>
   </ul>
   <h4>Other Literature Sources</h4>
   ...
</div>

So the parent selectors do return HTML with lots of <a> tags. This also appears to be valid HTML.

More experimenting reveals that lxml does not like the xmlns attribute on the opening div, for some reason.

How can I ignore this in lxml, and just parse it like regular HTML?

UPDATE: Trying ns_clean, still failing:

    parser = etree.XMLParser(ns_clean=True)
    tree = etree.parse(StringIO(response.content), parser)
    sel = CSSSelector('#maincontent .rprt_all a')
    print sel(tree)

Solution

You need to handle namespaces, including an empty one.

Working solution:

from pyquery import PyQuery as pq
import requests


response = requests.get('http://www.ncbi.nlm.nih.gov/pubmed/?term=The%20cost-effectiveness%20of%20mirtazapine%20versus%20paroxetine%20in%20treating%20people%20with%20depression%20in%20primary%20care')

namespaces = {'xi': 'http://www.w3.org/2001/XInclude', 'test': 'http://www.w3.org/1999/xhtml'}
links = pq('#maincontent .linkoutlist test|a', response.content, namespaces=namespaces)
for link in links:
    print link.attrib.get("title", "No title")

Prints titles of all links matching the selector:

Full text at publisher's site
No title
Free resource
Free resource
Free resource
Free resource

Or, just set the parser to "html" and forget about namespaces:

links = pq('#maincontent .linkoutlist a', response.content, parser="html")
for link in links:
    print link.attrib.get("title", "No title")