[XML-SIG] finding the NS URI for a prefix in a DOM

[Alexandre]

On Fri, Jul 19, 2002 at 11:29:34AM -0400, Fred L. Drake, Jr. wrote:
> 
> Alexandre writes:
>  > I have a silly DOM question. I'm using 4DOM on this one, but this may
>  > change later. 
>  > 
>  > What is the best way of finding the nsuri of a namespace given a prefix
>  > to which the nsuri could be mapped?
> 
> My own preference would be to use the lookupNamespaceURI() method on a
> node, but that would imply we have a Level 3 DOM.  I suspect that
> minidom will eventually provide this in some form.  ;-)

It's a long time since I've looked at the DOM TR drafts...

> 
> I don't think we have a good way to do that now, but it could be done
> in a DOM-independent way by walking up the tree looking at namespace
> declarations.

What I've decided to use is XPath:

from xml.xpath import Evaluate
def prefix_to_nsuri(node):
    map = {}
    ns_nodes = Evaluate('namespace::node()',node)
    for ns in ns_nodes:
        map[ns.localName]=ns.value
    return map

This works very well, and only needs a slight change to be able to get
the ns uri for one given prefix. 

Alexandre Fayolle
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