使用元类构建 Python 枚举类

Question

出于某种原因，在周日早上，我觉得我正在编写的科学图书馆需要以下内容：

class PolarityType(type):

    """Metaclass to construct polarity types. Supports conversion to float and int."""

    def __float__(cls):

        return int(cls)

    def __int__(cls):

        return cls.P

class Polarity(metaclass=PolarityType):

    """Base class to build polarity."""

    P = 0

class PositivePolarity(Polarity):

    """Positive polarity."""

    P = 1

class NegativePolarity(Polarity):

    """Negative polarity."""

    P = -1

>>> float(NegativePolarity)

>>> -1.0

基本上不是传递参数polarity='POSITIVE'和检查字符串，也因为我使用类型提示，我希望它是强类型的，我写了上面的代码。

这是否有意义，是否有更简单/更清洁/更好的方法来实现相同的结果？

Answer 1

您的解决方案有效，但是否有特殊原因不使用enum？import enumclass Polarity(enum.Enum):&nbsp; &nbsp; POSITIVE: float = 1.0&nbsp; &nbsp; NEGATIVE: float = -1.0&nbsp; &nbsp; def __float__(cls):&nbsp; &nbsp; &nbsp; &nbsp; return self.value&nbsp; &nbsp; def __int__(cls):&nbsp; &nbsp; &nbsp; &nbsp; return int(self.value)print(Polarity.NEGATIVE, type(Polarity.NEGATIVE))# Polarity.NEGATIVE <enum 'Polarity'>print(type(Polarity.NEGATIVE.value), Polarity.NEGATIVE.value)# <class 'float'> -1.0print(type(float(Polarity.NEGATIVE)), float(Polarity.NEGATIVE))# <class 'float'> -1.0