Here’s how to adapt the accepted answer to the question Abstract Enum Class using ABCMeta and EnumMeta to create the kind of abstract Enum
class you want:
from abc import abstractmethod, ABC, ABCMeta
from enum import auto, Flag, EnumMeta
class ABCEnumMeta(ABCMeta, EnumMeta):
def __new__(mcls, *args, **kw):
abstract_enum_cls = super().__new__(mcls, *args, **kw)
# Only check abstractions if members were defined.
if abstract_enum_cls._member_map_:
try: # Handle existence of undefined abstract methods.
absmethods = list(abstract_enum_cls.__abstractmethods__)
if absmethods:
missing = ', '.join(f'{method!r}' for method in absmethods)
plural="s" if len(absmethods) > 1 else ''
raise TypeError(
f"cannot instantiate abstract class {abstract_enum_cls.__name__!r}"
f" with abstract method{plural} {missing}")
except AttributeError:
pass
return abstract_enum_cls
class TranslateableFlag(Flag, metaclass=ABCEnumMeta):
@classmethod
@abstractmethod
def base(cls):
pass
def translate(self):
base = self.base()
if self in base:
return base[self]
else:
ret = []
for basic in base:
if basic in self:
ret.append(base[basic])
return " | ".join(ret)
class Students1(TranslateableFlag):
ALICE = auto()
BOB = auto()
CHARLIE = auto()
ALL = ALICE | BOB | CHARLIE
@classmethod
def base(cls):
return {Students1.ALICE: "Alice", Students1.BOB: "Bob",
Students1.CHARLIE: "Charlie"}
# Abstract method not defined - should raise TypeError.
class Students2(TranslateableFlag):
ALICE = auto()
BOB = auto()
CHARLIE = auto()
ALL = ALICE | BOB | CHARLIE
# @classmethod
# def base(cls):
# ...
Result:
Traceback (most recent call last):
...
TypeError: cannot instantiate abstract class 'Students2' with abstract method 'base'