Outputting an "Unused" XML Namespace Using ElementTree

Question

I am using Python 3.2 xml.etree.ElementTreeand trying to generate XML as follows:

<XnaContent xmlns:data="Model.Data">
    <Asset Type="data:MyData">
        ...

The format is out of my control (this is XNA). Note that the dataXML namespace is never used to qualify elements or attributes, but rather qualify attribute values ​​for XNA. My code is as follows:

root = Element('XnaContent')
ET.register_namespace('data', 'Model.Data') 
asset = SubElement(root, 'Asset', {"Type": "data:MyData"})

However, the output looks like (pretty printed by me):

<XnaContent>
    <Asset Type="data:MyData">
        ...
    </Asset>
</XnaContent>

How can I get the dataXML namespace included in the output?

Answer 1

>>>print ET.tostring(doc, pretty_print=True)
<XnaContent>
  <Asset Type="data:MyData"/>
  <Asset Type="data:MyData"/>
</XnaContent>
>>> tree=ET.ElementTree(doc)
>>> root=tree.getroot()
>>> nsmap=root.nsmap
>>> nsmap['data']="ModelData"
>>> new_root = ET.Element(root.tag, nsmap=nsmap)
>>> print ET.tostring(new_root, pretty_print=True)
<XnaContent xmlns:data="ModelData"/>
>>> new_root[:] = root[:]
>>> print ET.tostring(new_root, pretty_print=True)
<XnaContent xmlns:data="ModelData">
  <Asset Type="data:MyData"/>
  <Asset Type="data:MyData"/>
</XnaContent>

Answer 2

import xml.etree.ElementTree as ET
content = '''
<XnaContent>
  <Asset Type="data:MyData"/>
  <Asset Type="data:MyData"/>
</XnaContent>'''
doc = ET.fromstring(content)
ET.register_namespace('data','ModelData')
tree = ET.ElementTree(doc)
root = tree.getroot()
root.tag = '{ModelData}XnaContent'
print(ET.tostring(root, method = 'xml'))

gives

<data:XnaContent xmlns:data="ModelData">
      <Asset Type="data:MyData" />
      <Asset Type="data:MyData" />
    </data:XnaContent>