Re: [xml] xml Digest, Vol 128, Issue 2

 Sorry, that pseudocode makes little sense to me.

suppose you have an XML document with nodes in a given namespace

<a xmlns="http://foo/bar";>

if you want to be able to select the b element in that document
"//b" wont work you need to define a namespace prefix in your
XPath context (whatever it is) and then prepare the xpath query
using that context. Example with xmllint shell command:

thinkpad:~/XML -> cat tst.xml
<a xmlns="http://foo/bar";>
thinkpad:~/XML -> xmllint --shell tst.xml
/ > setns foobar=http://foo/bar
/ > xpath //b
Object is a Node Set :
Set contains 0 nodes:
/ > xpath //foobar:b
Object is a Node Set :
Set contains 1 nodes:
/ > 

it would be exactly the same if your document used an explicit namespace
instead of a default name, even if the prefix is different e.g

<fb:a xmlns:fb="http://foo/bar";>

  Hope this helps,


On Tue, Feb 10, 2015 at 11:56:40AM -0500, Alex Boese wrote:
I'm thinking it should look something like this, assuming Python language:

Import xmlsec
Import libxml2


    def test_get_xml_fragment(self,xpath,ns):
         ret = None
         context = self.doc.xpathNewContext()
         if ns is None:

         res = context.xpathEval(xpath)
         i = 0
         for node in res:
              print i,':',node
              i = i + 1

Please note there is an object in the mix, and I can get the whole to work great without namespaces. One 
good example of how Python should be handling namespaces in this case would be great. Even telling me it's 
forever broken...this too would be good to know. (Also, this is not an ideal example...I get this. I want 
something that hobbles before I get something hat soars.)

Thanks in advance.

Sent from my Planet

Message: 2
Date: Fri, 30 Jan 2015 09:03:40 -0600
From: Ross Reedstrom <reedstrm rice edu>
To: xml gnome org
Subject: Re: [xml] Xpath issues with libxml2
Message-ID: <20150130150340 GA28262 rice edu>
Content-Type: text/plain; charset=us-ascii

Alex -
With out examples of what you've tried, it's hard to diagnose the problem.
However, seeing 'namespaces' and 'never returns anything' makes me think you're
having issues with the default namespace concept. While XML documents have a
default namespace, XPaths do not. Once you use namespaces in an xml document,
all your xpaths will need to use namespace declarations for all the path parts,
even for tags that are defaulted in the document. So, you'll need to declare
a namespace prefix that matches the default namespace in the doc. Give us
a small example that you've tried that doesn't work, we'll fix it.


On Fri, Jan 30, 2015 at 08:44:15AM -0500, Alex Boese wrote:
Forgive me if this is a deprecated approach (as I am not fully aware), but I was utilizing "default" 
libxml2 bindings (not lxml) in Python to retrieve xml fragments via xpath functions. Normally this seems 
to work fine, but with namespace declarations this seems especially problematic as nothing ever returns 
and nothing errors. Would it be possible to confirm what correct functions and order of operations would 
be for this? Even if the example is C, I can translate that to Python.

Ross Reedstrom, Ph.D.                                 reedstrm rice edu
Systems Engineer & Admin, Research Scientist        phone: 713-348-6166
Connexions                    fax: 713-348-3665
Rice University MS-375, Houston, TX 77005
GPG Key fingerprint = F023 82C8 9B0E 2CC6 0D8E  F888 D3AE 810E 88F0 BEDE


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Daniel Veillard      | Open Source and Standards, Red Hat
veillard redhat com  | libxml Gnome XML XSLT toolkit | virtualization library

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