Problematic `xmlns:ns0` with `write_xml`

[alexreg]

Take an SVG like the following.

<svg xmlns:ns0="http://www.w3.org/1999/xlink" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ev="http://www.w3.org/2001/xml-events">
    ...
</svg>

If I then load and write this SVG back to a file, as follows.

svg = SVG.parse("input.svg")
svg.write_xml("output.svg")

Then I get something like this.

<svg xmlns:ns0="http://www.w3.org/1999/xlink" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ev="http://www.w3.org/2001/xml-events">
    ...
</svg>

This is invalid XML, since the same namespace is defined with two different names (ns0 and xlink), and causes problems with some other programs that read SVGs.

[saardrimer]

Have a look at:

https://docs.python.org/3/library/xml.etree.elementtree.html#xml.etree.ElementTree.register_namespace

which will register the namespace and quite possibly resolve your issue.