8000 gh-103629: Update typing.Unpack docs in compliance with PEP 692 by franekmagiera · Pull Request #103894 · python/cpython · GitHub
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gh-103629: Update typing.Unpack docs in compliance with PEP 692 #103894

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merged 2 commits into from
Apr 26, 2023
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gh-103629: Update typing.Unpack docs in compliance with PEP 692 #103894

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GH-103629: Update typing.Unpack docs in compliance with PEP 692
franekmagiera Apr 26, 2023
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GH-103629: Update NEWS and whatsnew with PEP-692 information
franekmagiera Apr 26, 2023
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GH-103629: Update typing.Unpack docs in compliance with PEP 692
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@franekmagiera
franekmagiera committed Apr 26, 2023
commit 9529f871de63c265e4b194c0f38662ed010c2c9e
24 changes: 22 additions & 2 deletions Doc/library/typing.rst
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Expand Up @@ -98,6 +98,9 @@ annotations. These include:
*Introducing* :data:`LiteralString`
* :pep:`681`: Data Class Transforms
*Introducing* the :func:`@dataclass_transform<dataclass_transform>` decorator
* :pep:`692`: Using ``TypedDict`` for more precise ``**kwargs`` typing
*Introducing* a new way of typing ``**kwargs`` with :data:`Unpack` and
:data:`TypedDict`
* :pep:`698`: Adding an override decorator to typing
*Introducing* the :func:`@override<override>` decorator

Expand Down Expand Up @@ -1417,8 +1420,10 @@ These are not used in annotations. They are building blocks for creating generic
tup: tuple[Unpack[Ts]]

In fact, ``Unpack`` can be used interchangeably with ``*`` in the context
of types. You might see ``Unpack`` being used explicitly in older versions
of Python, where ``*`` couldn't be used in certain places::
of :class:`typing.TypeVarTuple <TypeVarTuple>` and
:class:`builtins.tuple <tuple>` types. You might see ``Unpack`` being used
explicitly in older versions of Python, where ``*`` couldn't be used in
certain places::

# In older versions of Python, TypeVarTuple and Unpack
# are located in the `typing_extensions` backports package.
Expand All @@ -1428,6 +1433,21 @@ These are not used in annotations. They are building blocks for creating generic
tup: tuple[*Ts] # Syntax error on Python <= 3.10!
tup: tuple[Unpack[Ts]] # Semantically equivalent, and backwards-compatible

``Unpack`` can also be used along with :class:`typing.TypedDict` for typing
``**kwargs`` in a function signature::

from typing import TypedDict, Unpack

class Movie(TypedDict):
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4 space tab would've been more consistent.

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3 spaces are the convention in the docs.

name: str
year: int

# This function expects two keyword arguments - `name` of type `str`
# and `year` of type `int`.
def foo(**kwargs: Unpack[Movie]): ...

See :pep:`692` for more details on using ``Unpack`` for ``**kwargs`` typing.

.. versionadded:: 3.11

.. class:: ParamSpec(name, *, bound=None, covariant=False, contravariant=False)
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