Python Parse XML feed error: XPathEvalError: Undefined namespace prefix

Question

I'm trying to process an XML file, but I'm getting this error:

XPathEvalError: Undefined namespace prefix

in this line:

print "category =", item.xpath("./g:google_product_category")

This is is the XML file:

<rss xmlns:g="http://base.google.com/ns/1.0" version="2.0">
<channel>
<title>example.net.br</title>
<link>http://www.example.net.br/</link>
<description>Data feed description.</description>
<item>
<title>
<![CDATA[
example
]]>
</title>
<link>
<![CDATA[
example
]]>
</link>
<description>
<![CDATA[
example]]>
</description>
<g:google_product_category>
<![CDATA[
example
]]>
</g:google_product_category>
...

This is my code:

headers = { 'User-Agent' : 'Mozilla/5.0' }
req = urllib2.Request(feed_url, None, headers)
file = urllib2.urlopen(req).read()

file = etree.fromstring(file)
for item in file.xpath('/rss/channel/item'):
    print "title =", item.xpath("./title/text()")[0]
    print "link =", item.xpath("./link/text()")[0]
    print "description =", item.xpath("./description/text()")[0]
    print "category =", item.xpath("./g:google_product_category")

How can I fix this?

Answer 1

The xpath method accepts an additional parameter: namespaces

Could you try to modify the line as follows:

print "category =", item.xpath("./g:google_product_category", namespaces={'g': 'http://base.google.com/ns/1.0'})

Source of the information available here