Using an interface class for a constant "container" would often be handy but it
might be an inappropriate use of interface classes.

I would argue that it is appropriate, but that's probably related to my experience with languages other than Python.

FTR, I do often put
constants in an "interfaces.py" module at module scope (if there are more than
one related, sometimes in a dictionary or within a non-interface class
statement) in order to not feel I need to create some "constants.py" module.
Maybe we could just agree that doing so isn't some sort of violation of intent?

That works, too.

Seeing as I how I don't see much interest, I'll consider this something not worth pursuing further.

Thanks,
Chris