custom match-case rules

matchmeta.py

class MatchMeta(type):
    def __instancecheck__(cls, inst):
        return cls.isinstance(inst)

def matching(fn):
    class cls(metaclass=MatchMeta):
        isinstance = fn
    return cls


@matching
def even(number):
    return isinstance(number, int) and number % 2 == 0


match 22:
    case even():
        print("even!")
    case _:
        print("not")