__ne__是否应在Python中实现为__eq__的否定形式? [英] Should __ne__ be implemented as the negation 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.我应该这样实现 __ ne __ 作为对 __ eq __ 的否定，还是一个坏主意?

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. Should I implement __ne__ as the negation of __eq__ as such or is it a bad idea?

class A:

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

    def __eq__(self, other):
        return self.state == other.state

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

推荐答案

是的，这很好.实际上，文档敦促您定义 __ ne __ __ eq __ 时的code>:

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

没有隐含的关系在比较运算符之间.这 x == y 的真相并不表示 x！= y 是错误的.因此，在定义时 __ eq __()，还应该定义 __ ne __()，以便操作员能够按预期进行操作.

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(例如本例)，它与否定 __ eq __ 的结果一样简单，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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