How to make a python class automatic conversion in Mathematica

[oovm]

I know that class who inherits the WLSerializable class and overrides the to_wl method can be automatically converted in Mathematica.

But how to modify the existing python class?

For example, how to extend symbols in sympy.

[DbxDev]

You should take a look at this section of the documentation: https://reference.wolfram.com/language/WolframClientForPython/docpages/advanced_usages.html#extending-serialization-writing-an-encoder

It explain how one can define encoders for arbitrary classes. Please let me know if that answers your question.

[oovm]

Nice work, very easy to use!