Python“是"声明:发生了什么? [英] Python "is" statement: what is happening?

问题描述

我很惊讶

[] 不是 []

评估为 True.

这段代码发生了什么?not 和 is 语句到底在做什么?

解决方案

a is not b 是一个特殊的运算符，它等价于 not a is b.>

运算符a is b 如果a 和b 绑定到同一个对象，则返回True，否则返回False.当您创建两个空列表时，您会得到两个不同的对象，因此 is 返回 False(因此 is not 返回 True).

I was quite surprised when

[] is not []

evaluated to True.

What is happening in this code? What really not and is statements are doing?

解决方案

a is not b is a special operator which is equivalent to not a is b.

The operator a is b returns True if a and b are bound to the same object, otherwise False. When you create two empty lists you get two different objects, so is returns False (and therefore is not returns True).

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