[lxml-dev] xpath on newly created elements

[Doug Winter]

Stefan Behnel wrote:
> Well, you can currently create them this way, but it doesn't give you what you
> want. Maybe we should catch the case where ':' is contained in a tag name and
> raise an exception instead (it won't give you well-formed XML anyway). That
> way, it would be clear that this can't work.
> 
> When you create elements with namespaces, use the Clark notation.

Thanks for the clarification.  What threw me is that serialising a tag 
with a colon in it works fine, and this all feels quite natural:

 >>> nsmap = {'test': 'http://test.com'}
 >>> e = etree.Element('test:foo', nsmap=nsmap)
 >>> e2 = etree.fromstring(etree.tostring(e))
 >>> e.xpath("/test:foo", nsmap)
[]
 >>> e2.xpath("/test:foo", nsmap)
[<Element {http://test.com}foo at b793d5a4>]

I'd expect the round trip to produce something identical, which I guess 
is where I got confused.  I think it may be worth raising an exception 
on tags with colons, since it is a bit surprising.

Cheers,

Doug.

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