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Created on 2020-09-23 23:33 by slebedev, last changed 2022-04-11 14:59 by admin. This issue is now closed.
| Pull Requests | |||
|---|---|---|---|
| URL | Status | Linked | Edit |
| PR 22394 | closed | BTaskaya, 2020-09-24 06:51 | |
| Messages (5) | |||
|---|---|---|---|
| msg377435 - (view) | Author: Sergei Lebedev (slebedev) | Date: 2020-09-23 23:33 | |
Reproducer: [x for x in [] if lambda: x] This parses fine in 3.8, but doesn't parse in 3.9 because the grammar expects a disjunction after if in for_if_clause [*]. While this change has zero practical significance, I think it might be useful to maintain a list of such changes for tooling authors (who might need to support multiple Python versions). [*]: https://github.com/python/cpython/blob/68526fe258da8c01196fd7cf48e8e5f1280bf8fd/Grammar/python.gram#L523 |
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| msg377511 - (view) | Author: Terry J. Reedy (terry.reedy) *  |
Date: 2020-09-25 23:20 | |
After adding parens, >>> [x for x in [] if (lambda: x)] [] |
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| msg377514 - (view) | Author: Guido van Rossum (gvanrossum) * |
Date: 2020-09-26 00:27 | |
I propose not to fix this, since it is pointless (a lambda is always truthy). We can call it out in What's New in 3.9 -- as a very small footnote. :-) |
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| msg377545 - (view) | Author: Pablo Galindo Salgado (pablogsal) * |
Date: 2020-09-26 21:49 | |
I concur with Guido: it makes the grammar slightly more complex for no gain. Also, the originally allowed rule does not allow *any* lambda but only the ones that are simple, which is a special case that makes it even more complex. In any case you can use parentheses to break this limitation. Like Guido, I propose to add a very small comment to What's New in 3.9 |
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| msg377546 - (view) | Author: Guido van Rossum (gvanrossum) * |
Date: 2020-09-26 23:36 | |
Okay, let's close this. |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:35 | admin | set | github: 86014 |
| 2020-09-26 23:36:40 | gvanrossum | set | status: open -> closed resolution: wont fix messages: + msg377546 stage: patch review -> resolved |
| 2020-09-26 21:49:42 | pablogsal | set | messages: + msg377545 |
| 2020-09-26 00:27:58 | gvanrossum | set | messages: + msg377514 |
| 2020-09-25 23:20:56 | terry.reedy | set | nosy:
+ terry.reedy messages: + msg377511 |
| 2020-09-24 06:51:50 | BTaskaya | set | keywords:
+ patch nosy: + BTaskaya pull_requests: + pull_request21434 stage: patch review |
| 2020-09-24 06:46:26 | serhiy.storchaka | set | nosy:
+ gvanrossum, benjamin.peterson, serhiy.storchaka, pablogsal |
| 2020-09-23 23:33:02 | slebedev | create | |