[XML-SIG] Reconsidering NamespaceErr on '' and None

[Rich Salz]

I will answer my own question.

cDomlette uses empty string for the no namespace
	<foo id='fid'>
I have to call getAttributeNS('', 'id')

ZSI supports run-time DOM selection, so now my DOM-portable code looks
like this:
  try:
    from xml.dom import EMPTY_NAMESPACE
    _empty_nsuri_list = [ EMPTY_NAMESPACE ]
    if '' not in _empty_nsuri_list: __empty_nsuri_list.append('')    
    if None not in _empty_nsuri_list: __empty_nsuri_list.append(None)
  except:
    _empty_nsuri_list = [ None, '' ]
  def _find_attr(E, attr):
    for nsuri in _empty_nsuri_list:
        try:
            v = E.getAttributeNS(nsuri, attr)
            if v: return v
        except: pass
    return None

that's pretty horrible.

If PyXML 0.7 silently converts '' to None, then I can go back to
  _find_attr = lambda E, attr: E.getAttributeNS(None, attr) or \
	E.getAttributeNS('', attr)
which has a performance hit if the attribute is not found.

I am not sure which is better.
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