可以使用Python枚举中的命名参数吗？ [英] Can named arguments be used with Python enums?

问题描述

示例：

class Planet(Enum):

    MERCURY = (mass: 3.303e+23, radius: 2.4397e6)

    def __init__(self, mass, radius):
        self.mass = mass       # in kilograms
        self.radius = radius   # in meters

参考： https://docs.python.org/3/library/enum.html#planet

为什么要这样做？如果构造函数列表中有几个基本类型（int，bool），那么使用命名参数就会很好。

Why do I want to do this? If there are a few primitive types (int, bool) in the constructor list, it would be nice to used named arguments.

推荐答案

虽然您不能以枚举的形式使用命名参数，但您可以使用 namedtuple mixin：

While you can't use named arguments the way you describe with enums, you can get a similar effect with a namedtuple mixin:

from collections import namedtuple
from enum import Enum

Body = namedtuple("Body", ["mass", "radius"])

class Planet(Body, Enum):

    MERCURY = Body(mass=3.303e+23, radius=2.4397e6)
    VENUS   = Body(mass=4.869e+24, radius=6.0518e6)
    EARTH   = Body(mass=5.976e+24, radius=3.3972e6)
    # ... etc.

...在我心里很清洁，因为你不需要写一个 __ init __ 方法。

... which to my mind is cleaner, since you don't have to write an __init__ method.

使用示例：

>>> Planet.MERCURY
<Planet.MERCURY: Body(mass=3.303e+23, radius=2439700.0)>
>>> Planet.EARTH.mass
5.976e+24
>>> Planet.VENUS.radius
6051800.0

请注意，根据文档，混合类型必须在枚举之前出现在基地的顺序。

Note that, as per the docs, "mix-in types must appear before Enum itself in the sequence of bases".

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