Preserve existing namespaces when overwriting an XML file with ElementTree and Python

Question

I have an XML file in the following format

<?xml version="1.0" encoding="utf-8"?>
<foo>
   <bar>
      <bat>1</bat>
   </bar>
   <a>
      <b xmlns="urn:schemas-microsoft-com:asm.v1">
         <c>1</c>
      </b>
   </a>
</foo>

I want to change the value of bat to '2' and change the file to this:

<?xml version="1.0" encoding="utf-8"?>
<foo>
   <bar>
      <bat>2</bat>
   </bar>
   <a>
      <b xmlns="urn:schemas-microsoft-com:asm.v1">
         <c>1</c>
      </b>
   </a>
</foo>

I open this file by doing this

tree = ET.parse(filePath)
root = tree.getroot()

Then I change the value of bat to "2" and save the file as follows:

tree.write(filePath, "utf-8", True, None, "xml")

The bat value is successfully changed to 2, but the XML file now looks like this.

<?xml version="1.0" encoding="utf-8"?>
<foo xmlns:ns0="urn:schemas-microsoft-com:asm.v1">
   <bar>
      <bat>2</bat>
   </bar>
   <a>
      <ns0:b>
         <ns0:c>1</ns0:c>
      </ns0:b>
   </a>
</foo>

To fix a problem with the namespace named ns0 before analyzing the document

follow these steps:

ET.register_namespace('', "urn:schemas-microsoft-com:asm.v1")

This will get rid of the ns0 namespace, but now the xml file looks like this:

<?xml version="1.0" encoding="utf-8"?>
<foo xmlns="urn:schemas-microsoft-com:asm.v1">
   <bar>
      <bat>2</bat>
   </bar>
   <a>
      <b>
         <c>1</c>
      </b>
   </a>
</foo>

What should I do to get the result I need?

Answer 1

, xml.etree.ElementTree . xml.etree xml.etree xml , . , .

, , . , render.

from xml.etree import ElementTree as ET
from re import findall, sub

def render(root, buffer='', namespaces=None, level=0, indent_size=2, encoding='utf-8'):
    buffer += f'<?xml version="1.0" encoding="{encoding}" ?>\n' if not level else ''
    root = root.getroot() if isinstance(root, ET.ElementTree) else root
    _, namespaces = ET._namespaces(root) if not level else (None, namespaces)
    for element in root.iter():
        indent = ' ' * indent_size * level
        tag = sub(r'({[^}]+}\s*)*', '', element.tag)
        buffer += f'{indent}<{tag}'
        for ns in findall(r'{[^}]+}', element.tag):
            ns_key = ns[1:-1]
            if ns_key not in namespaces: continue
            buffer += ' xmlns' + (f':{namespaces[ns_key]}' if namespaces[ns_key] != '' else '') + f'="{ns_key}"'
            del namespaces[ns_key]
        for k, v in element.attrib.items():
            buffer += f' {k}="{v}"'
        buffer += '>' + element.text.strip() if element.text else '>'
        children = list(element)
        for child in children:
            sep = '\n' if buffer[-1] != '\n' else ''
            buffer += sep + render(child, level=level+1, indent_size=indent_size, namespaces=namespaces)
        buffer += f'{indent}</{tag}>\n' if 0 != len(children) else f'</{tag}>\n'
    return buffer

render() xml :

data =\ 
'''<?xml version="1.0" encoding="utf-8"?>
<foo>
   <bar>
      <bat>1</bat>
   </bar>
   <a>
      <b xmlns="urn:schemas-microsoft-com:asm.v1">
         <c>1</c>
      </b>
   </a>
</foo>'''

root = ET.ElementTree(ET.fromstring(data))
ET.register_namespace('', "urn:schemas-microsoft-com:asm.v1")
print(render(root))

, :

<?xml version="1.0" encoding="utf-8" ?>
<foo>
  <bar>
    <bat>1</bat>
  </bar>
  <a>
    <b xmlns="urn:schemas-microsoft-com:asm.v1">
      <c>1</c>
    </b>
  </a>
</foo>