from xml.sax.saxutils import XMLGenerator

g = XMLGenerator(encoding='utf8')
STREAM_NAMESPACE = 'http://etherx.jabber.org/streams'
CLIENT_NAMESPACE = 'jabber:client'
g.startDocument()
g.startPrefixMapping('stream', STREAM_NAMESPACE)
g.startPrefixMapping('client', CLIENT_NAMESPACE)
g.startElementNS( 
    (STREAM_NAMESPACE, 'stream'), 'stream',
    {(None,'xmlns'): CLIENT_NAMESPACE}
    )

Dies with:
Traceback (most recent call last):
  File "tst.py", line 11, in ?
    g.startElementNS( 
  File "/System/Library/Frameworks/Python.framework/
Versions/2.3/lib/python2.3/xml/sax/saxutils.py", line 124, in 
startElementNS
    name = self._current_context[name[0]] + ":" + name[1]
KeyError: 'x'


Changing the end of XMLGenerator.startElementNS to the 
following makes it work the way I expect:

        for (name, value) in attrs.items():
            if name[0] is None:
                name = name[1]
            else:
                name = self._current_context[name[0]] + ":" + 
name[1]
            self._out.write(' %s=%s' % (name, 
quoteattr(value)))
        self._out.write('>')

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This method also appears to have trouble emmitting tags without a 
namespace prefix:

import xml.sax
import xml.sax.handler
import xml.sax.saxutils
x = '''<?xml version="1.0"?><mechanisms xmlns='urn:ietf:
params:xml:ns:xmpp-sasl'
>'''
parser = xml.sax.make_parser()
parser.setFeature(xml.sax.handler.feature_namespaces, True)
parser.setContentHandler(xml.sax.saxutils.XMLGenerator())
parser.feed(x)

dies with:
Traceback (most recent call last):
  File "tst.py", line 30, in ?
    parser.feed(x)
  File "/System/Library/Frameworks/Python.framework/Versions/
2.3/lib/python2.3/xml/sax/expatreader.py", line 207, in feed
    self._parser.Parse(data, isFinal)
  File "/System/Library/Frameworks/Python.framework/Versions/
2.3/lib/python2.3/xml/sax/expatreader.py", line 337, in 
start_element_ns
    AttributesNSImpl(newattrs, qnames))
  File "/System/Library/Frameworks/Python.framework/Versions/
2.3/lib/python2.3/xml/sax/saxutils.py", line 116, in startElementNS
    name = self._current_context[name[0]] + ":" + name[1]
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'



I've attached my current replacement startElementNS method 
which appears to fix both this and the previous issue.

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I don't understand your second example; it uses saxutils to
parse a file.  What's it got to do with XMLGenerator?

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Never mind my previous comment; I just noticed the
setContentHandler call.

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Please provide your changes in the form of a patch.

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This issue lasts for 2.5 years already. I feel like it is
somewhat stalled.

The processing of XML namespaces in saxutils.XMLGenerator is
so blatantly broken that I wonder if it ever has been tested
at all. I wrote down a simple smoke test for it:


import sys
from xml import sax
from xml.sax.saxutils import XMLGenerator
from StringIO import StringIO

tests = [
("No namespace, no attributes",     "<a/>"),
("No namespace, with attributes",   "<a b='c'/>"),
("Empty prefix, no attributes",     "<a xmlns='qux'/>"),
("Empty prefix, unprefixed attributes", "<a xmlns='qux'
b='c'/>"),
("Prefixed, no attributes",         "<my:a xmlns:my='qux'/>"),
("Prefixed, unprefixed attributes", "<my:a xmlns:my='qux'
b='c'/>"),               
("Prefixed, prefixed attributes",   "<my:a xmlns:my='qux'
my:b='c'/>"),
]
          
for (caption, testdoc) in tests:
    try:
        parser = sax.make_parser()
        parser.setFeature(sax.handler.feature_namespaces, 1)
        parser.setContentHandler(XMLGenerator(StringIO()))
        parser.parse(StringIO(testdoc))
        print caption, "- OK"
    except StandardError, e:
        print caption, "- FAILED:", e.__class__.__name__


With the current version of saxutils (as of Python 2.4.1), I
get 4 failures out of 7. Stuart Bishop's patch fixes the
issue; could someone commit it please?

This is now fixed in r53754 and r53755.