SemiEnum

semienum.py

class SemiEnumMeta(type):
    def __new__(mcs, name, bases, class_dict):
        class_ = super().__new__(mcs, name, bases, class_dict)
        class_.__value_mapping = {}
        for name, value in class_dict.items():
            if name.startswith("__"):
                continue
            instance = class_(value)
            setattr(class_, name, instance)
            class_.__value_mapping[value] = instance
        return class_

    def __call__(self, value):
        res = self.__value_mapping.get(value)
        if res:
            return res
        return super().__call__(value)


class SemiEnum(metaclass=SemiEnumMeta):
    def __init__(self, value):
        self.value = value


class ErrorType(SemiEnum):
    x = 1


print(ErrorType(1) is ErrorType.x)
print(ErrorType(2).value)