gh-86482: Document assignment expression need for ()s by terryjreedy · Pull Request #23291 · python/cpython

terryjreedy · 2020-11-15T07:44:55Z

The list should cover most places where an assignment sub-expression
must be wrapped in parentheses. Judging from the statement docs,
only a couple of statements do not require that they be wrapped.

Issue: Walrus Operator in list index #86482

The list should cover most places where an assignment sub-expression must be wrapped in parentheses. Judging from the statement docs, only a couple of statements do not require that they be wrapped.

lysnikolaou · 2020-11-16T23:29:18Z

This PR probably needs to be updated to reflect the recent changes introduced in #23317 and #23319. Sorry @terryjreedy!

terryjreedy · 2020-11-17T05:14:55Z

These are changes I hoped to be able to make ;-). I will add the new in 3.10 item for indexes.

github-actions · 2020-12-18T00:28:35Z

This PR is stale because it has been open for 30 days with no activity.

JelleZijlstra

@terryjreedy are you still interested in landing this? A few older comments were never applied.

terryjreedy · 2022-04-06T09:50:46Z

I somehow missed finishing this and would like it updated and merged. The doc is needed; someone just posted code to pydev that was missing required ()s. However, I just discovered that I have been recently de-authorized from merging anything. Jelle, you have been doing great with doc patches, so it would be fine with me if you finished this without waiting for that problem to be fixed.

JelleZijlstra · 2022-04-06T14:20:41Z

I have been recently de-authorized from merging anything

Pablo had turned off merges for everyone during the 3.11.0a7 release, but merges are allowed now again.

JelleZijlstra

This looks good to me now. I'll merge it in a few days unless other people on the PR have more feedback.

gvanrossum · 2022-10-03T21:53:33Z

I'm fine with documenting this more precisely, and the wording here looks fine. However, I don't have the time to review the facts -- I hope that Lysandros and Jelle can make sure that the claim made in the text is true (or as close to true as reasonable without spelling out the entire grammar).

lysnikolaou · 2022-10-03T22:19:33Z

 process(chunk)

+Assignment expressions must be surrounded by parentheses when used
+as sub-expressions in slicing, conditional, lambda,


Unparenthesized assignment expressions in slices were implemented in #23317, so they are allowed since 3.10. Also, assignment expression need to parenthesized in assert and with statements.

Unparenthesized walruses are allowed in index expressions but not slices. This is current 3.12:
>>> x[y:=3] Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'x' is not defined >>> x[y:=3:z:=4] File "<stdin>", line 1 x[y:=3:z:=4] ^ SyntaxError: invalid syntax

Correct! I mixed up indexes/slices. Sorry!

miss-islington · 2022-10-06T19:24:20Z

Thanks @terryjreedy for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.11.
🐍🍒⛏🤖

bedevere-bot · 2022-10-06T19:24:27Z

GH-97986 is a backport of this pull request to the 3.11 branch.

…-23291) Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> (cherry picked from commit 2b5f136) Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

bedevere-bot · 2022-10-06T19:24:30Z

GH-97987 is a backport of this pull request to the 3.10 branch.

…-23291) Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> (cherry picked from commit 2b5f136) Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> (cherry picked from commit 2b5f136) Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

* main: fixespythongh-96078: os.sched_yield release the GIL while calling sched_yield(2). (pythongh-97965) pythongh-65961: Do not rely solely on `__cached__` (pythonGH-97990) pythongh-97850: Remove the open issues section from the import reference (python#97935) Docs: pin sphinx-lint (pythonGH-97992) pythongh-94590: add signatures to operator itemgetter, attrgetter, methodcaller (python#94591) Add Pynche's move to the What's new in 3.11 (python#97974) pythongh-97781: Apply changes from importlib_metadata 5. (pythonGH-97785) pythongh-86482: Document assignment expression need for ()s (python#23291) pythongh-97943: PyFunction_GetAnnotations should return a borrowed reference. (python#97949) pythongh-94808: Coverage: Test that maximum indentation level is handled (python#95926)

* main: pythonGH-97002: Prevent `_PyInterpreterFrame`s from backing more than one `PyFrameObject` (pythonGH-97996) pythongh-97973: Return all necessary information from the tokenizer (pythonGH-97984) fixespythongh-96078: os.sched_yield release the GIL while calling sched_yield(2). (pythongh-97965) pythongh-65961: Do not rely solely on `__cached__` (pythonGH-97990) pythongh-97850: Remove the open issues section from the import reference (python#97935) Docs: pin sphinx-lint (pythonGH-97992) pythongh-94590: add signatures to operator itemgetter, attrgetter, methodcaller (python#94591) Add Pynche's move to the What's new in 3.11 (python#97974) pythongh-97781: Apply changes from importlib_metadata 5. (pythonGH-97785) pythongh-86482: Document assignment expression need for ()s (python#23291) pythongh-97943: PyFunction_GetAnnotations should return a borrowed reference. (python#97949)

…3291) Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> (cherry picked from commit 2b5f136) Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

terryjreedy added 2 commits November 15, 2020 02:38

bpo-42316: Document assignment expression need for ()s
ff66b33
The list should cover most places where an assignment sub-expression must be wrapped in parentheses. Judging from the statement docs, only a couple of statements do not require that they be wrapped.

Add 'be'
09653d7

terryjreedy added docs Documentation in the Doc dir needs backport to 3.8 labels Nov 15, 2020

terryjreedy requested a review from gvanrossum November 15, 2020 07:44

terryjreedy self-assigned this Nov 15, 2020

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This was referenced Nov 16, 2020
bpo-42374: Allow unparenthesized walrus in genexps #23319
Merged
bpo-42316: Allow unparenthesized walrus operator in indexes #23317
Merged

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vbarbaresi mentioned this pull request Oct 24, 2021
Error trying to format line with parameter assignment and generator psf/black#2551
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Merge branch 'main' into walrus
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JelleZijlstra merged commit 2b5f136 into python:mainOct 6, 2022

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Brando753mannequin mentioned this pull request Oct 6, 2022
Walrus Operator in list index #86482
Closed

miss-islington added a commit that referenced this pull request Oct 6, 2022
gh-86482: Document assignment expression need for ()s (GH-23291)
4aa2ebc
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> (cherry picked from commit 2b5f136) Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

miss-islington added a commit that referenced this pull request Oct 6, 2022
gh-86482: Document assignment expression need for ()s (GH-23291)
b7487df
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> (cherry picked from commit 2b5f136) Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

mpage pushed a commit to mpage/cpython that referenced this pull request Oct 11, 2022
pythongh-86482: Document assignment expression need for ()s (python#2…
ff0d621
…3291) Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

pablogsal pushed a commit that referenced this pull request Oct 22, 2022
gh-86482: Document assignment expression need for ()s (GH-23291)
cc10a8e
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> (cherry picked from commit 2b5f136) Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

terryjreedy deleted the walrus branch December 17, 2023 00:04

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