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[Python-Dev] <int> in <str>


It's because when the rhs is a string, 'in' tests for a substring rather
than simple containment. E.g. "ab" in "abc" gives True. So here 'in' is not
a collection membership, it only operates on two strings.

On Tue, Apr 3, 2018 at 4:34 PM, Ethan Furman <ethan at stoneleaf.us> wrote:

> This behavior was recently brought to my attention [1]:
>
> --> 1 in 'hello'
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> TypeError: 'in <string>' requires string as left operand, not int
>
> However, in any other collection (set, dict, list, tuple, etc), the answer
> would be False.
>
> Does anyone remember the reason why an exception is raised in the string
> instance instead of returning False?
>
> --
> ~Ethan~
>
>
>
> [1] https://bugs.python.org/msg314900
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-- 
--Guido van Rossum (python.org/~guido)
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