Python布尔比较和是

2022-01-19 00:00:00 python boolean

问题描述

Python 3.6.2 控制台:

Python 3.6.2 console:

>>> 11 > 0 is True
False

但是

>>> 0 is True
False
>>> 11 > False
True

那么，为什么 11 >0 是真 是 假?

So, why 11 > 0 is True is False?

解决方案

这是一个比较链接 因为 > 和 is 都是比较运算符.

This is an example of comparison chaining since both > and is are comparison operators.

比较可以任意链接，例如，x <y <= z 是等价的到 x <y 和 y <= z，除了 y 只计算一次(但在这两个当 x x 时根本不计算 zy 被发现是假的).

Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent to x < y and y <= z, except that y is evaluated only once (but in both cases z is not evaluated at all when x < y is found to be false).

形式上，如果 a, b, c, ..., y, z 是表达式，而 op1, op2, ..., opN 是比较运算符，则 a op1 b op2 c ... y opN z 等价于a op1 b and b op2 c and ... y opN z，除了每个表达式是最多评估一次.

Formally, if a, b, c, …, y, z are expressions and op1, op2, …, opN are comparison operators, then a op1 b op2 c ... y opN z is equivalent to a op1 b and b op2 c and ... y opN z, except that each expression is evaluated at most once.

因此，它等价于:

>>> (11 > 0) and (0 is True)
False

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