Extend multiple classes

[adriangb]

Is there any way to do the equivalent of:

class MyBaseException(BaseException):
    pass

class MyException(MyBaseException, Exception):
    pass

It seems like you can't have more than one base in extends

[davidhewitt]

In principle we could support multiple base types, however as far as I know the Python bases need to have "compatible layouts" and that's not currently something designed for in our PyCell type.

I think if we supported it, it should be opt-in; nanobind chose to drop multiple inheritance support to simplify compared to pybind11.

[phoerious]

I would be interested in this as well. I have multiple mixin bases and have to duplicate all my subclass implementations and doc strings, because I can inherit only from a single class. This is made worse by the fact that I cannot use macros inside #[pymethods], so I actually have to copy-paste all my pymethods to all subclasses.