问题描述
有人可以解释以下测试背后的原因吗??
Can somebody explain the reasoning behind the following tests ??
>>> 1 and True
True
>>> {'foo': 'Foo'} and True
True
>>> {} and True
{}
>>>
推荐答案
在布尔运算的上下文中，以及当控制流语句使用表达式时，以下值被解释为 false:False、None、数字零所有类型，以及空字符串和容器(包括字符串、元组、列表、字典、集合和frozensets).所有其他值都被解释为 true.
In the context of Boolean operations, and also when expressions are used by control flow statements, the following values are interpreted as false: False, None, numeric zero of all types, and empty strings and containers (including strings, tuples, lists, dictionaries, sets and frozensets). All other values are interpreted as true.
表达式 x 和 y 首先计算 x；如果 x 为假，则返回其值；否则，计算 y 并返回结果值.
The expression x and y first evaluates x; if x is false, its value is returned; otherwise, y is evaluated and the resulting value is returned.
表达式 x 或 y 首先计算 x；如果 x 为真，则返回其值；否则，计算 y 并返回结果值.
The expression x or y first evaluates x; if x is true, its value is returned; otherwise, y is evaluated and the resulting value is returned.
如需进一步参考，请阅读有关布尔运算的更多信息:http://docs.python.org/reference/expressions.html#boolean-operations
For further reference read more on Boolean operations: http://docs.python.org/reference/expressions.html#boolean-operations
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