bpo-46066: Deprecate kwargs syntax for TypedDict definitions by 97littleleaf11 · Pull Request #31126 · python/cpython (original) (raw)

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Surely this is a breaking change — even if type-checkers only understand the literal-dict assignment-based syntax, I'm not sure we can change the runtime behaviour like this without a deprecation period.

Yeah, it changes the typing module. However I seldom see this syntax in real-world projects since we already have class based one.

I am not really familiar with the cpython developing period. It's not a big deal since neither mypy nor other widely-used type checkers implement this feature and I barely see this syntax in real world projects.

Yeah, it changes the typing module. However I seldom see this syntax in real-world projects since we already have class based one.

I appreciate that — but given that this is a change to the stdlib, I think the standard deprecation policy probably still applies :)

For now, I think I would:

• Change the docs to state that this is deprecated in 3.11, will be removed in 3.13, and probably won't be understood by type checkers like mypy.
• Change the runtime behaviour to emit a warning if a user tries to construct a TypedDict with the kwargs-based syntax.

Here's an example of a previous PR deprecating features, that you could look to as an example: #23064

Co-authored-by: AlexWaygood Alex.Waygood@Gmail.com

97littleleaf11 changed the titlebpo-46066: Remove kwargs syntax for TypedDict definition bpo-46066: Deprecate kwargs syntax for TypedDict definitions

Feb 8, 2022

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It feels absurd to bring this up (sorry!!), but: I think "Jingchen Ye" should go before "Ka-Ping Yee", if we're keeping this list alphabetised.

Also, it looks like there's some trailing whitespace in some of the documentation changes you've made, which is making the documentation-related tests fail -- could you possibly fix those issues?

@AlexWaygood Thanks for your reviews! btw, it seems that CI reports wrong line number about the trailing whitespace.

@AlexWaygood Thanks for your reviews!

No worries, it's a good PR!

btw, it seems that CI reports wrong line number about the trailing whitespace.

Huh — no idea what might be causing that :)

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LGTM

As this is a deprecation of an existing feature, I think it probably warrants a mention in "What's New in Python 3.11". I think @JelleZijlstra is planning on doing a PR for that document mentioning a bunch of recent changes to typing, though, so perhaps he'll be kind enough to include a mention of this as well :)

@gvanrossum, could we possibly get the full test suite run on this PR, please? :)

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I can't stand "firstly" and "secondly" for some reason. :-(

I can't stand "firstly" and "secondly" for some reason. :-(

How about "The first one" and "The other one"?

How about "The first one" and "The other one"?

Probably, a bullet list will be better. Like this:

[...] syntactic forms:

• using a literal dict as the second argument:

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

• using keyword arguments:

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

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Here's a concrete wording suggestion that avoids "Firstly" and "Secondly"

Comment on lines 1391 to 1393

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Thanks for this!

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I was just hoping to see “first“ and “second”. No “ly” needed, these are flat adverbs.

In a few days Jelle can likely merge this himself. :-)