为什么〜True导致-2？ [英] Why does ~True result in -2?

问题描述

在Python控制台中：

In Python console:

~True

给我：

-2

为什么？有人可以用二进制给我解释这个特殊情况吗？

Why? Can someone explain this particular case to me in binary?

推荐答案

int（True）是 1 。

1 是：

00000001

和〜1 是：

11111110

-2 ：//en.wikipedia.org/wiki/Two%27s_complement rel = noreferrer>双向补数 ¹

Which is -2 in Two's complement¹

¹ 翻转所有位，将结果加1，并将结果解释为幅度的二进制表示，并添加一个负号（因为数字以1开头） ：

¹ Flip all the bits, add 1 to the resulting number and interpret the result as a binary representation of the magnitude and add a negative sign (since the number begins with 1):

11111110 → 00000001 → 00000010 
         ↑          ↑ 
       Flip       Add 1

该数字为2，但由于 MSB 为1。

Which is 2, but the sign is negative since the MSB is 1.

值得一提的是：

想想布尔，您会发现它本质上是数字-它有两个值， True 和 False ，它们只是自定义整数1和0的版本，它们的打印方式不同。它们是整数类型 int 的子类。

Think about bool, you'll find that it's numeric in nature - It has two values, True and False, and they are just "customized" versions of the integers 1 and 0 that only print themselves differently. They are subclasses of the integer type int.

所以它们的行为与1完全相同和0，除了 bool 将 str 和 repr 重新定义为

So they behave exactly as 1 and 0, except that bool redefines str and repr to display them differently.

>>> type(True)
<class 'bool'>
>>> isinstance(True, int)
True

>>> True == 1
True
>>> True is 1  # they're still different objects
False

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