创建抽象枚举类

Question

我试图用一个抽象方法创建一个抽象枚举（Flag）。 我的最终目标是能够基于我定义的基本枚举创建复合枚举的字符串表示。 我可以在不把类抽象化的情况下获得这个功能。在

这是基本的Flag类和一个示例实现：

from enum import auto, Flag

class TranslateableFlag(Flag):
    @classmethod
    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 Students(TranslateableFlag):
    ALICE = auto()
    BOB = auto()
    CHARLIE = auto()
    ALL = ALICE | BOB | CHARLIE

    @classmethod
    def base(cls):
        return {Students.ALICE: "Alice", Students.BOB: "Bob",
                Students.CHARLIE: "Charlie"}

示例用法如下：

^{pr2}$

由于元类冲突，切换到TranslateableFlag(Flag, ABC)失败。 （我不明白这篇文章-Abstract Enum Class using ABCMeta and EnumMeta，所以我不确定它是否回答了我的问题）。在

我想得到这样的功能：

@abstractclassmethod
@classmethod
    def base(cls):
        pass

有可能做到这一点吗？在

Answer 1

下面是如何将accepted answer调整为问题Abstract Enum Class using ABCMeta and EnumMeta，以创建您想要的抽象Enum类：

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)
        try:  # Handle existence of undefined abstract methods.
            absmethods = list(abstract_enum_cls.__abstractmethods__)
            absmethods_str = ', '.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} {absmethods_str}")
        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"}


class Students2(TranslateableFlag):
    ALICE = auto()
    BOB = auto()
    CHARLIE = auto()
    ALL = ALICE | BOB | CHARLIE

# Abstract method not defined - should raise TypeError.
#    @classmethod
#    def base(cls):
#        ...

结果：

^{pr2}$

Answer 2

如果目标只是更改Students1的__str__输出，则不需要使用抽象类：

from enum import auto, Flag
from functools import reduce

class TranslateableFlag(Flag):

    def __init__(self, value):
        self.translated = self.name.title()

    def __str__(self):
        cls = self.__class__
        total = self._value_
        i = 1
        bits = set()
        while i <= total:
            bits.add(i)
            i *= 2
        members = [m for m in cls if m._value_ in bits]
        return '%s' % (
                ' | '.join([str(m.translated) for m in members]),
                )

class Students1(TranslateableFlag):
    ALICE = auto()
    BOB = auto()
    CHARLIE = auto()
    ALL = ALICE | BOB | CHARLIE

使用中：

^{pr2}$