Mailman 3 - Typing-sig

Opened and changed typing issues week 2023-W21
by Typing Bot May 29, 2023

May 29, 2023

The following is an overview of all issues and pull requests in the typing repository on GitHub with the label 'topic: feature' that were opened or updated last week, excluding closed issues. --------------------------------------------------- The following issues and pull requests were opened last week: #1405 Generic ParamSpec in subclass definitions opened by @alanhdu https://github.com/python/typing/issues/1405 --------------------------------------------------- All issues and pull requests with the label 'topic: feature' can be viewed under the following URL: https://github.com/python/typing/issues?q=label%3A%22topic%3A+feature%22

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Release: typing-extensions 4.6.0
by Jelle Zijlstra May 23, 2023

May 23, 2023

I just released typing-extensions 4.6.0: https://pypi.org/project/typing-extensions/4.6.0/ This release comes with documentation at https://typing-extensions.readthedocs.io/en/latest/ (previously typing-extensions was documented only through its README). In addition, there is a large number of additions and improvements. Copying from the changelog: - `typing_extensions` is now documented at https://typing-extensions.readthedocs.io/en/latest/. Patch by Jelle Zijlstra. - Add `typing_extensions.Buffer`, a marker class for buffer types, as proposed by PEP 688. Equivalent to `collections.abc.Buffer` in Python 3.12. Patch by Jelle Zijlstra. - Backport two CPython PRs fixing various issues with `typing.Literal`: https://github.com/python/cpython/pull/23294 and https://github.com/python/cpython/pull/23383. Both CPython PRs were originally by Yurii Karabas, and both were backported to Python >=3.9.1, but no earlier. Patch by Alex Waygood. A side effect of one of the changes is that equality comparisons of `Literal` objects will now raise a `TypeError` if one of the `Literal` objects being compared has a mutable parameter. (Using mutable parameters with `Literal` is not supported by PEP 586 or by any major static type checkers.) - `Literal` is now reimplemented on all Python versions <= 3.10.0. The `typing_extensions` version does not suffer from the bug that was fixed in https://github.com/python/cpython/pull/29334. (The CPython bugfix was backported to CPython 3.10.1 and 3.9.8, but no earlier.) - Backport [CPython PR 26067](https://github.com/python/cpython/pull/26067) (originally by Yurii Karabas), ensuring that `isinstance()` calls on protocols raise `TypeError` when the protocol is not decorated with `@runtime_checkable`. Patch by Alex Waygood. - Backport several significant performance improvements to runtime-checkable protocols that have been made in Python 3.12 (see https://github.com/python/cpython/issues/74690 for details). Patch by Alex Waygood. A side effect of one of the performance improvements is that the members of a runtime-checkable protocol are now considered “frozen” at runtime as soon as the class has been created. Monkey-patching attributes onto a runtime-checkable protocol will still work, but will have no impact on `isinstance()` checks comparing objects to the protocol. See ["What's New in Python 3.12"]( https://docs.python.org/3.12/whatsnew/3.12.html#typing) for more details. - `isinstance()` checks against runtime-checkable protocols now use `inspect.getattr_static()` rather than `hasattr()` to lookup whether attributes exist (backporting https://github.com/python/cpython/pull/103034). This means that descriptors and `__getattr__` methods are no longer unexpectedly evaluated during `isinstance()` checks against runtime-checkable protocols. However, it may also mean that some objects which used to be considered instances of a runtime-checkable protocol on older versions of `typing_extensions` may no longer be considered instances of that protocol using the new release, and vice versa. Most users are unlikely to be affected by this change. Patch by Alex Waygood. - Backport the ability to define `__init__` methods on Protocol classes, a change made in Python 3.11 (originally implemented in https://github.com/python/cpython/pull/31628 by Adrian Garcia Badaracco). Patch by Alex Waygood. - Speedup `isinstance(3, typing_extensions.SupportsIndex)` by >10x on Python <3.12. Patch by Alex Waygood. - Add `typing_extensions` versions of `SupportsInt`, `SupportsFloat`, `SupportsComplex`, `SupportsBytes`, `SupportsAbs` and `SupportsRound`. These have the same semantics as the versions from the `typing` module, but `isinstance()` checks against the `typing_extensions` versions are >10x faster at runtime on Python <3.12. Patch by Alex Waygood. - Add `__orig_bases__` to non-generic TypedDicts, call-based TypedDicts, and call-based NamedTuples. Other TypedDicts and NamedTuples already had the attribute. Patch by Adrian Garcia Badaracco. - Add `typing_extensions.get_original_bases`, a backport of [`types.get_original_bases`]( https://docs.python.org/3.12/library/types.html#types.get_original_bases), introduced in Python 3.12 (CPython PR https://github.com/python/cpython/pull/101827, originally by James Hilton-Balfe). Patch by Alex Waygood. This function should always produce correct results when called on classes constructed using features from `typing_extensions`. However, it may produce incorrect results when called on some `NamedTuple` or `TypedDict` classes that use `typing.{NamedTuple,TypedDict}` on Python <=3.11. - Constructing a call-based `TypedDict` using keyword arguments for the fields now causes a `DeprecationWarning` to be emitted. This matches the behaviour of `typing.TypedDict` on 3.11 and 3.12. - Backport the implementation of `NewType` from 3.10 (where it is implemented as a class rather than a function). This allows user-defined `NewType`s to be pickled. Patch by Alex Waygood. - Fix tests and import on Python 3.12, where `typing.TypeVar` can no longer be subclassed. Patch by Jelle Zijlstra. - Add `typing_extensions.TypeAliasType`, a backport of `typing.TypeAliasType` from PEP 695. Patch by Jelle Zijlstra. - Backport changes to the repr of `typing.Unpack` that were made in order to implement [PEP 692](https://peps.python.org/pep-0692/) (backport of https://github.com/python/cpython/pull/104048). Patch by Alex Waygood. Please report any issues at https://github.com/python/typing_extensions/issues.

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PEP 695: "Type Parameter Syntax" accepted
by Alfonso L. Castaño May 22, 2023

May 22, 2023

I haven't seen it published in this mailing list so sharing for visibility: https://discuss.python.org/t/pep-695-type-parameter-syntax/21646/92 https://peps.python.org/pep-0695/ Thank you very much for your effort Eric, and congratulations. I am personally very excited about this PEP!

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Opened and changed typing issues week 2023-W20
by Typing Bot May 22, 2023

May 22, 2023

No issues or pull requests with the label 'topic: feature' were opened or updated last week in the typing repository on GitHub. All issues and pull requests with the label 'topic: feature' can be viewed under the following URL: https://github.com/python/typing/issues?q=label%3A%22topic%3A+feature%22

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Why isn't a specialized generic class a subclass of its non-specialized version?
by Kevin Millikin May 16, 2023

May 16, 2023

I'm working on implementing narrowing for `issubclass` checks and I find the runtime behavior of this kind of surprising: >>> issubclass(list[int], list) False Why isn't list[int] a subclass of list? It seems inconsistent with the runtime behavior of this: >>> x: list[int] = [1, 2, 3] >>> isinstance(x, list) True -- [image: logo] Kevin Millikin Software Engineer kmillikin(a)deepmind.com If you received this email in error, please do not forward it to anyone else (it may contain confidential or privileged information), erase all copies and attachments, and let me know that it has gone to the wrong person.

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Opened and changed typing issues week 2023-W19
by Typing Bot May 15, 2023

May 15, 2023

The following is an overview of all issues and pull requests in the typing repository on GitHub with the label 'topic: feature' that were opened or updated last week, excluding closed issues. --------------------------------------------------- The following issues and pull requests were updated last week: #213 Introduce an Intersection opened by @ilevkivskyi https://github.com/python/typing/issues/213 #1216 TypeVarTuple Transformations Before Unpack opened by @llchan https://github.com/python/typing/issues/1216 --------------------------------------------------- All issues and pull requests with the label 'topic: feature' can be viewed under the following URL: https://github.com/python/typing/issues?q=label%3A%22topic%3A+feature%22

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Backport PEP 695's `typing.TypeAliasType` via `typing-extensions`
by Adrian Garcia Badaracco May 14, 2023

May 14, 2023

PEP 695 introduces a new `typing.TypeAliasType` that is the runtime object that gets created when someone does `type MyList = list[T]` (see https://peps.python.org/pep-0695/#runtime-type-alias-class). I would like to propose this gets backported via `typing-extensions`. Backporting this in particular has advantages both for end users and libraries: - End users get to use this on older Python versions - Libraries that do runtime type introspection can support this without clunky if/else clauses or other hacks by relying on `typing-extensions` to take care of that like we already do for other things, of which PEP 593's `Annotated` is a good example because both cases require re-implementing large parts of `typing.py` e.g. to make `get_origin` function correctly. It would also be nice if type checkers recognized the usage `MyGenList = TypeAliasType("MyGenList", list[T], type_params=(T,))` as equivalent to `type MyGenList[T] = list[T]`, although users that want to use the backport with static type checking could always hack around this by using `if TYPE_CHECKING`: ```python from typing import TypeVar, TYPE_CHECKING from typing_extensions import TypeAliasType T =TypeVar('T') if TYPE_CHECKING: MyGenList = list[T] else: MyGenList = TypeAliasType("MyGenList", list[T], type_params=(T,)) ``` Or if they don't care about static type checking for this particular piece of code `# type: ignore` is always an option. So I don't think integration with static type checkers should be a blocker for backporting, but it would be nice to have for end users. I'll add some color as to why I want this backported. Pydantic, FastAPI, etc. have begun to heavily buy into using PEP 593's `Annotated` to replace a variety of hacks like `x: conint(gt=0)` or `x: int | None = Query(None)` with `x: Annotated[int, Gt(0)]` and `x: Annotated[int | None, Query()] = None` respectively. This is very powerful because it lets static type checkers work unencumbered by runtime typing information. It also enabled metadata to be part of type aliases: `PostiveInt = Annotated[int, Gt(0)]` and then `x: PositiveInt`. But not all is perfect with this setup. One of the issues is that this can become super verbose, I wish one could do something like `x: [int, Gt(0)]` or something, but that's a discussion for another day. The other issue is that these type aliases are anonymous: say you have `User = List[User]` as a type alias and then in *multiple* FastAPI endpoints you have `users: Users`. You'd hope that in your schema you get a single model named `Users` (or for the previous example `PositiveInt`). But FastAPI has no way of knowing the name of `Users`, that's just the identifier name and it gets lost at runtime. So it ends up creating multiple `List[User]` entries instead. The new type alias syntax/type lets us create named type aliases, which resolves this issue.

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Typing Summit @ PyCon US 2023
by S Pradeep Kumar May 9, 2023

May 9, 2023

Hello all, PyCon US 2023 is coming up! If you're attending, please join us at the Typing Summit, for its third annual edition since 2021. When: Thursday, April 20, 2023, 1-5 pm UT (GMT-6). Where: Room 253AB, Salt Palace Convention Center, Salt Lake City, Utah. Agenda and details: https://us.pycon.org/2023/events/typing-summit/ Agenda: - Introductions - The State of Python Typing - Jelle Zijlstra - Common Typing Pain Points from User Questions - Alex Waygood - PEP 649 and runtime __annotations__ - Carl Meyer - Using Type Hints at Runtime - Samuel Colvin - Standardization across type checkers - Kevin Millikin - Adding Type Annotations using MonkeyType - Carl Meyer - Adding Type Annotations using Static Information - Steven Troxler - Steering Council Panel, moderated by Guido van Rossum All the talks will be recorded. We will share the video link here after the summit. Unfortunately, there won't be an official livestream. Thanks to everyone who has put in the time and effort to prepare a topic for presentation and discussion. Excited to see everyone there! Best, Jelle and Pradeep

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Opened and changed typing issues week 2023-W18
by Typing Bot May 8, 2023

May 8, 2023

The following is an overview of all issues and pull requests in the typing repository on GitHub with the label 'topic: feature' that were opened or updated last week, excluding closed issues. --------------------------------------------------- The following issues and pull requests were opened last week: #1399 Feature request: Allow unpacking of type variable bound to typed dict opened by @NeilGirdhar https://github.com/python/typing/issues/1399 #1400 Consider adding a "TopLevel" keyword that stands in for the top level bound of a corresponding type variable opened by @NeilGirdhar https://github.com/python/typing/issues/1400 --------------------------------------------------- The following issues and pull requests were updated last week: #213 Introduce an Intersection opened by @ilevkivskyi https://github.com/python/typing/issues/213 #769 [feature] Get the type from a variable opened by @Dimitri-WEI-Lingfeng https://github.com/python/typing/issues/769 --------------------------------------------------- All issues and pull requests with the label 'topic: feature' can be viewed under the following URL: https://github.com/python/typing/issues?q=label%3A%22topic%3A+feature%22

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What is @staticmethod in Protocols?
by Kevin Millikin May 5, 2023

May 5, 2023

Our typechecker stumbled across this Protocol: https://github.com/google/jax/blob/1c7f8efce64ca2927fd3f2de9250063d7c5fe09e… This is a Protocol with a @staticmethod. PEP 544 ( https://peps.python.org/pep-0544/) says only: "Static methods, class methods, and properties are equally allowed in protocols." The PEP doesn't say anything at all about what it *means* to have one of these in a structural supertype. Structurally, consider a Protocol like: class P(Protocol): @staticmethod def foo(x: str) -> int: ... The protocol has an attribute named `foo` with type `(x: str) -> int`. @staticmethod is an implementation detail which does not affect the structure of P. The protocol should be satisfied by *any* type with an attribute named `foo` with type `(x: str) -> int`. (Similarly, if a protocol requires a @property getter you could satisfy it with a field, etc.) Test: ``` from typing import Protocol class P(Protocol): @staticmethod def foo(x: str) -> int: ... class A: @staticmethod def foo(x: str) -> int: return len(x) class B: def foo(self, x: str) -> int: return len(x) class Str2Int(Protocol): def __call__(self, x: str) -> int: ... class C: foo: Str2Int def __init__(self): self.foo = lambda x: 0 def test(x: P) -> None: return test(A()) test(B()) test(C()) ``` Pyright agrees with me. $ pyright --version pyright 1.1.306 $ pyright static-protocols.py 0 errors, 0 warnings, 0 informations Mypy does not :( : $ mypy --version mypy 1.2.0 (compiled: yes) $ mypy static-protocols.py static-protocols.py:27: error: Argument 1 to "test" has incompatible type "B"; expected "P" [arg-type] static-protocols.py:27: note: Protocol member P.foo expected class or static method static-protocols.py:28: error: Argument 1 to "test" has incompatible type "C"; expected "P" [arg-type] static-protocols.py:28: note: Protocol member P.foo expected class or static method Found 2 errors in 1 file (checked 1 source file) -- [image: logo] Kevin Millikin Software Engineer kmillikin(a)deepmind.com If you received this email in error, please do not forward it to anyone else (it may contain confidential or privileged information), erase all copies and attachments, and let me know that it has gone to the wrong person.

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