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Created on 2019-08-01 16:23 by zhusu.china, last changed 2022-04-11 14:59 by admin. This issue is now closed.
| Messages (4) | |||
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| msg348864 - (view) | Author: Su Zhu (zhusu.china) | Date: 2019-08-01 16:23 | |
The filter become empty after serving as an argument of list(). Python 3.6.7 (default, Oct 22 2018, 11:32:17) [GCC 8.2.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> a = filter(lambda x:x, [1,2,3]) >>> list(a) [1, 2, 3] >>> list(a) [] |
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| msg348865 - (view) | Author: Rémi Lapeyre (remi.lapeyre) * | Date: 2019-08-01 16:26 | |
Hi Su Zhu, this is expected, as per the documentation, filter returns an iterable and not a list. The first `list(a)` consumes the iterable so it is empty when doing the second `list(a)`. You can see the same behavior when creating an iterable manually: >>> a = iter([1, 2, 3]) >>> list(a) [1, 2, 3] >>> list(a) [] If you need to keep the result in a list, you can do: >>> a = list(filter(lambda x:x, [1,2,3])) |
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| msg348866 - (view) | Author: Ned Deily (ned.deily) *  |
Date: 2019-08-01 16:30 | |
https://docs.python.org/3/library/functions.html#filter |
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| msg348882 - (view) | Author: Su Zhu (zhusu.china) | Date: 2019-08-02 01:51 | |
I see. Thank you very much! |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:18 | admin | set | github: 81920 |
| 2019-08-02 01:51:07 | zhusu.china | set | messages: + msg348882 |
| 2019-08-01 16:30:26 | ned.deily | set | status: open -> closed nosy: + ned.deily messages: + msg348866 resolution: not a bug stage: resolved |
| 2019-08-01 16:26:32 | remi.lapeyre | set | nosy:
+ remi.lapeyre messages: + msg348865 |
| 2019-08-01 16:23:02 | zhusu.china | create | |