extending python enums

extendable.py

from enum import IntFlag, EnumMeta


class BaseExt(IntFlag):
    __extending__ = None

    @classmethod
    def append(cls, members: list[tuple[str, int]]):
        _members = BaseExt(cls.__name__, members)
        for member in _members:
            cls._member_names_.append(member.name)
            cls._value2member_map_[member.value] = member
            cls._member_map_[member.name] = member


class Extendable(EnumMeta):
    def __subclasscheck__(cls, sub):
        return issubclass(sub, cls.__bases__[0])

    def __new__(cls, name, bases, kwds, **kwargs):
        ext = kwargs.get("extending", None)
        extends = [(m.name, m.value) for m in ext] if ext else []
        new_cls = BaseExt(
            name, [(k, v) for k, v in kwds.items() if not k.startswith("_")] + extends
        )
        new_cls.__extending__ = ext if ext else None
        return new_cls


class First(BaseExt, metaclass=Extendable):
    B = 0x0
    C = 0x1
    D = 0x2
    E = 0x4
    F = 0x8
    G = 0x10
    H = 0x20
    I = 0x40


class Second(
    BaseExt,
    extending=First,
    metaclass=Extendable,
):
    BLIND = 0x80
    DYING = 0x100


First.append([("J", 1000)])