我是否应该在__eq__中用python实现__ne__？ [英] Should I implement __ne__ in terms of __eq__ in Python?

问题描述

我有一个要覆盖 __ eq __ 方法的类。我也应该重写 __ ne __ 方法似乎很有意义，但是在其中实现 __ ne __ 是否有意义 __ eq __ 这样的术语？

I have a class where I want to override the __eq__ method. It seems to make sense that I should override the __ne__ method as well, but does it make sense to implement __ne__ in terms of __eq__ as such?

class A:

    def __init__(self, attr):
        self.attr = attr

    def __eq__(self, other):
        return self.attr == other.attr
    
    def __ne__(self, other):
        return not self.__eq__(other)

还是Python使用这些方法的方式使我不满意？

Or is there something that I am missing with the way Python uses these methods that makes this not a good idea?

推荐答案

是的，这很好。实际上，文档敦促您定义 __ne __ 定义 __ eq __ 时：

Yes, that's perfectly fine. In fact, the documentation urges you to define __ne__ when you define __eq__:

比较运算符之间没有隐含的关系
。 x == y 的
真相并不表示 x！= y
是假。因此，在定义
__ eq __（）时，还应定义 __ ne __（），以便操作员将

There are no implied relationships among the comparison operators. The truth of x==y does not imply that x!=y is false. Accordingly, when defining __eq__(), one should also define __ne__() so that the operators will behave as expected.

在很多情况下（例如这种情况），只要将 __ eq __ ，但并非总是如此。

In a lot of cases (such as this one), it will be as simple as negating the result of __eq__, but not always.

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