Python3 Enum with a separate class for storing constants

enumc.py

from collections import OrderedDict


class EnumMeta(type):
    def __init__(cls, name, bases, attrs):
        super(EnumMeta, cls).__init__(name, bases, attrs)
        if 'Consts' not in attrs:
            cls.Consts = type(
                'Consts',
                (Enum.Consts, ),
                dict(__module__=cls.__module__, _related_enum_class=cls)
            )


class EnumConstsMeta(type):
    _related_enum_class = None
    values = ()

    @classmethod
    def __prepare__(mcs, cls, bases):
        return OrderedDict()

    def __init__(cls, name, bases, attrs):
        super(EnumConstsMeta, cls).__init__(name, bases, attrs)
        if cls._related_enum_class is not None:
            cls._related_enum_class.Consts.values = tuple(
                val for val in attrs.values() if isinstance(val, cls._related_enum_class)
            )


class Enum(metaclass=EnumMeta):
    class Consts(metaclass=EnumConstsMeta):
        pass

    @classmethod
    def get_all(cls):
        return cls.Consts.values


class SmallNum(Enum):
    def __init__(self, num):
        self._num = num

    def __repr__(self):
        return 'SmallNum(%r)' % self._num


class SmallNumConsts(SmallNum.Consts):
    ZERO = SmallNum(0)
    ONE = SmallNum(1)
    TWO = SmallNum(2)
    THREE = SmallNum(3)
    FOUR = SmallNum(4)


print(SmallNum.get_all())