gh-86482: Document assignment expression need for ()s #23291
Conversation
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.
terryjreedy
added
docs
|
This PR probably needs to be updated to reflect the recent changes introduced in #23317 and #23319. Sorry @terryjreedy! |
|
These are changes I hoped to be able to make ;-). I will add the new in 3.10 item for indexes. |
|
This PR is stale because it has been open for 30 days with no activity. |
There was a problem hiding this comment.
@terryjreedy are you still interested in landing this? A few older comments were never applied.
|
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. |
Pablo had turned off merges for everyone during the 3.11.0a7 release, but merges are allowed now again. |
serhiy-storchaka
added
needs backport to 3.10
github-actions
bot
removed
the
stale
|
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). |
| @@ -1766,6 +1766,12 @@ Or, when processing a file stream in chunks: | |||
| while chunk := file.read(9000): | |||
| process(chunk) | |||
|
|
|||
| Assignment expressions must be surrounded by parentheses when used | |||
| as sub-expressions in slicing, conditional, lambda, | |||
There was a problem hiding this comment.
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.
There was a problem hiding this comment.
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
There was a problem hiding this comment.
Correct! I mixed up indexes/slices. Sorry!
|
Thanks @terryjreedy for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.11. |
|
GH-97986 is a backport of this pull request to the 3.11 branch. |
|
GH-97987 is a backport of this pull request to the 3.10 branch. |
* main: fixes pythongh-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) fixes pythongh-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>
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.