XML is not the answer. It is not even the question. To paraphrase
Jamie Zawinski on regular expressions, "Some people, when confronted
with a problem, think “I know, I’ll use XML.” Now they have
two problems."
This is a different situation than in Java, because compared to Java
code, XML is agile and flexible. Compared to Python code, XML is a boat
anchor, a ball and chain. In Python, XML is something you use for
interoperability, not your core functionality, because you simply don't
need it for that.