Deprecate keyword args syntax for TypedDict definition

[97littleleaf11]

BPO	46066
Nosy	@gvanrossum, @JelleZijlstra, @tirkarthi, @sobolevn, @Fidget-Spinner, @AlexWaygood, @97littleleaf11
PRs	bpo-46066: Deprecate kwargs syntax for TypedDict definitions #31126 bpo-46066: catch DeprecationWarning #31428

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2022-02-17.03:26:40.796>
created_at = <Date 2021-12-13.15:36:57.408>
labels = ['type-bug', 'library', '3.11']
title = 'Deprecate keyword args syntax for TypedDict definition'
updated_at = <Date 2022-02-20.01:44:58.632>
user = 'https://github.com/97littleleaf11'

bugs.python.org fields:

activity = <Date 2022-02-20.01:44:58.632>
actor = 'JelleZijlstra'
assignee = 'none'
closed = True
closed_date = <Date 2022-02-17.03:26:40.796>
closer = 'JelleZijlstra'
components = ['Library (Lib)']
creation = <Date 2021-12-13.15:36:57.408>
creator = '97littleleaf11'
dependencies = []
files = []
hgrepos = []
issue_num = 46066
keywords = ['patch']
message_count = 11.0
messages = ['408458', '408476', '408547', '412990', '413013', '413014', '413016', '413379', '413531', '413535', '413562']
nosy_count = 7.0
nosy_names = ['gvanrossum', 'JelleZijlstra', 'xtreak', 'sobolevn', 'kj', 'AlexWaygood', '97littleleaf11']
pr_nums = ['31126', '31428']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue46066'
versions = ['Python 3.11']

[97littleleaf11]

According to the docs: https://docs.python.org/3/library/typing.html?#typing.TypedDict, there are two additional equivalent syntax for TypedDict definition.

Point2D = TypedDict('Point2D', x=int, y=int, label=str)
Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})

However, the former one is quite confusing since we have the total keyword arg for TypedDict. In addition, PEP-589(https://www.python.org/dev/peps/pep-0589/#id19) doesn't have this.

I think we could discard the definition syntax using keyword args in the doc.

[gvanrossum]

This is not really just a doc issue then, is it? Maybe we should just deprecate the feature?

[gvanrossum]

I recommend opening an issue here: https://github.com/python/typing/issues/new/choose

[AlexWaygood]

Just so that all the discussion related to this issue can be found in one place, here's a summary:

• After opening this ticket, OP opened an issue in the python/typing repository, where the idea of deprecating this syntax received many thumbs-up reactions, and where there were no dissenting voices: TypedDict alternative definition syntax with keyword args is confusing typing#981
• The initial impetus for this change was this mypy bug report: TypedDict using keywords causes "error: Too many arguments for TypedDict()" mypy#11555
• Mypy's policy since January 2020 has been that it would be more trouble than it's worth to attempt to support the kwargs-based syntax: TypedDict syntax variant with keyword arguments mypy#2492 (comment)

[gvanrossum]

Go ahead and send a or to deprecate it.--
--Guido (mobile)

[gvanrossum]

"PR"

[AlexWaygood]

@guido, OP already has — Jelle and I have both reviewed and approved it :)

[JelleZijlstra]

New changeset de6043e by 97littleleaf11 in branch 'main':
bpo-46066: Deprecate kwargs syntax for TypedDict definitions (GH-31126)
de6043e

[tirkarthi]

This change has introduced deprecation warning in tests

PYTHONWARNINGS=always ./python -Wall -X dev -m test.test_typing     
........................................................................................................................................................................................................................s................................................................................................................................................................................................./home/karthikeyan/stuff/python/cpython/Lib/test/test_typing.py:4589: DeprecationWarning: The kwargs-based syntax for TypedDict definitions is deprecated in Python 3.11, will be removed in Python 3.13, and may not be understood by third-party type checkers.
  TypedDict('Emp', _fields={'name': str, 'id': int})
./home/karthikeyan/stuff/python/cpython/Lib/test/test_typing.py:4602: DeprecationWarning: The kwargs-based syntax for TypedDict definitions is deprecated in Python 3.11, will be removed in Python 3.13, and may not be understood by third-party type checkers.
  TypedDict('Hi', x=1)
........................................

---

Ran 451 tests in 0.105s

OK (skipped=1)

[JelleZijlstra]

Thanks, I'll send a PR.

[JelleZijlstra]

New changeset 0a8a8e7 by Jelle Zijlstra in branch 'main':
bpo-46066: Check DeprecationWarning in test_typing (GH-31428)
0a8a8e7

[gvanrossum]

@labrys

Doesn't this cause issues for keys that are valid as keys but not as identifiers?

To the contrary, the deprecated syntax caused issues for such keys. The syntax that isn't deprecated works fine, e.g.

Point2D = TypedDict('Point2D', {'x': int, 'y': int, '$label$': str})

[labrys]

@gvanrossum Thanks for the quick response. I deleted my previous comment right after I posted it realizing I had entirely misread it as if the kwargs method was the one being retained.