IF语句(检查列表中的字符串)的行为异常 [英] IF statement (checking for a string in a list) behave weirdly

问题描述

这可能是一个愚蠢的问题，但是为什么这段代码的行为如此?

This will probably be a dumb question, but why does this piece of code behave like this?

>>> test = ['aaa','bbb','ccc']
>>> if 'ddd' or 'eee' in test:
...     print True
... 
True
>>> 

我期望在stdio上不打印任何内容，因为IF语句中没有任何字符串在列表中.

I was expecting nothing printed on the stdio, because none of the strings in the IF statement are in the list.

我想念什么吗?

推荐答案

if 'ddd' or 'eee' in test

评估为:

if ('ddd') or ('eee' in test):

因为非空字符串始终为True，所以or操作会短路并返回True.

as a non-empty string is always True, so or operations short-circuits and returns True.

>>> bool('ddd')
True

要解决此问题，您可以使用以下任一方法:

To solve this you can use either:

if 'ddd' in test or 'eee' in test:

或any:

if any(x in test for x in ('ddd', 'eee')):

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