Python布尔比较，现为 [英] Python boolean comparison and is

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 is True是False?

推荐答案

这是

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是等效的 到x < y and y <= z，只对y进行一次评估(但在两次评估中均 发现x < y为假时完全不评估z的情况.)

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).

通常，如果a, b, c, …, y, z是表达式，而op1, op2, …, opN是表达式 比较运算符，则a op1 b op2 c ... y opN z等效于 a op1 b and b op2 c and ... y opN z，除了每个表达式都是 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，它等效于:

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

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