Cannot write XML file with default namespace [duplicate]

Question

I'm writing a Python script to update Visual Studio project files. They look like this:

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" 
      xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
      ...

The following code reads and then writes the file:

import xml.etree.ElementTree as ET

tree = ET.parse(projectFile)
root = tree.getroot()
tree.write(projectFile,
           xml_declaration = True,
           encoding = 'utf-8',
           method = 'xml',
           default_namespace = "http://schemas.microsoft.com/developer/msbuild/2003")

Python throws an error at the last line, saying:

ValueError: cannot use non-qualified names with default_namespace option

This is surprising since I'm just reading and writing, with no editing in between. Visual Studio refuses to load XML files without a default namespace, so omitting it is not optional.

Why does this error occur? Suggestions or alternatives welcome.

Looks like this is a known bug. See bugs.python.org/issue17088 — WombatPM
– WombatPM, Commented Aug 20, 2013 at 16:19

Community · Accepted Answer · 2017-05-23 12:17:46Z

47

This is a duplicate to Saving XML files using ElementTree

The solution is to define your default namespace BEFORE parsing the project file.

ET.register_namespace('',"http://schemas.microsoft.com/developer/msbuild/2003")

Then write out your file as

tree.write(projectFile,
           xml_declaration = True,
           encoding = 'utf-8',
           method = 'xml')

You have successfully round-tripped your file. And avoided the creation of ns0 tags everywhere.

edited May 23, 2017 at 12:17

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answered Aug 20, 2013 at 17:05

WombatPM

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1 Comment

peter.slizik Over a year ago

This approach works. However, find('mytag', ns) and findall('mytag', ns) methods fail (they return an empty list of elements). It seems that they require a non-empty namespace name. Which is fine, unless you want to write() the XML file with an empty namespace prefix for elements in the default namespace. (Using Python 2.7.)

tdelaney · Accepted Answer · 2013-08-20 16:21:48Z

4

I think that lxml does a better job handling namespaces. It aims for an ElementTree-like interface but uses xmllib2 underneath.

>>> import lxml.etree
>>> doc=lxml.etree.fromstring("""<?xml version="1.0" encoding="utf-8"?>
... <Project ToolsVersion="4.0" DefaultTargets="Build" 
...       xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
...   <PropertyGroup>
...   </PropertyGroup>
... </Project>""")

>>> print lxml.etree.tostring(doc, xml_declaration=True, encoding='utf-8', method='xml', pretty_print=True)
<?xml version='1.0' encoding='utf-8'?>
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="4.0" DefaultTargets="Build">
  <PropertyGroup>
  </PropertyGroup>
</Project>

answered Aug 20, 2013 at 16:21

tdelaney

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3 Comments

Andomar Over a year ago

+1 Though it looks like lxml.etree does not come with Python for Windows, so I'll accept WombatPM's answer

tdelaney Over a year ago

@WombatPM's answer is great too but lxml is available for windows. You can use pip, easy_install and (I think) Active State's pypm... or just grab it from (pypi)[pypi.python.org/pypi/lxml/3.2.3].

WombatPM Over a year ago

I've used lxml as well. Both are good.

Andomar · Accepted Answer · 2015-06-15 21:25:14Z

0

This was the closest answer I could find to my problem. Putting the:

ET.register_namespace('',"http://schemas.microsoft.com/developer/msbuild/2003")

just before the parsing of my file did not work.

You need to find the specific namespace the xml file you are loading is using. To do that, I printed out the Element of the ET tree node's tag which gave me my namespace to use and the tag name, copy that namespace into:

ET.register_namespace('',"XXXXX YOUR NAMESPACEXXXXXX")

before you start parsing your file then that should remove all the namespaces when you write.

edited Jun 15, 2015 at 21:25

Andomar

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answered Jun 15, 2015 at 18:11

JMStudios.jrichardson

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