extendable.py

@@ -0,0 +1,50 @@
+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)])