Guido van Rossum firstname.lastname@example.org writes:
I can't see any implementation benefits from the requirement. It sounds like you can't either
If the requirement was extended to disallow multiple root classes, it would disambiguate the case of the class Z(str,Exception): It would be an error to raise an exception of class Z. Classes that only inherit from str would continue to operate as string exceptions, classes that inherit from Exception would be caught by their type - you couldn't have a class that is both.