RégisDécamps, 21.02.2012 17:11:

I understand that custom XML elements should inherit from `ElementBase`.

For instance, I can create

class FactVariable(etree.ElementBase): ''' Class that represents a XBRL fact variable.''' TAG = '{http://xbrl.org/2008/variable}factVariable'

@property def label(self): return self.attrib['{http://www.w3.org/1999/xlink}label']

@label.setter def label(self, value): self.attrib['{http://www.w3.org/1999/xlink}label'] = value

My problem is that when I create a XML tree and place such nodes, I get

<ns0:factVariable xmlns:ns0="http://xbrl.org/2008/variable" label="azerty"/>

**Question**: I want the namespace to be prefixed `va`, not `ns0`

What is your use case for that? I consider prefixes a serialisation detail that is best ignored.

How can I change that?

You can't currently set that on a per-element basis for custom element classes. It also wouldn't change much, because the prefixes are subject to tree normalisation operations, which means that they may still end up inheriting a prefix from a parent at some point. What you can do is to set the prefix on the root element, so that children can inherit it.

I also tried, without success

etree.register_namespace('va', 'http://xbrl.org/2008/variable')

Hmm, that should generally work, though. I wonder why it wouldn't... Stefan