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[3.6] bpo-28556: Clarify that Type[SomeTypeVar] is legal (GH-9585) #9591

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miss-islington merged 1 commit into from
Sep 26, 2018
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[3.6] bpo-28556: Clarify that Type[SomeTypeVar] is legal (GH-9585) #9591

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Clarify that Type[SomeTypeVar] is legal (GH-9585) 
Currently, the docs state that when doing `Type[X]`, X is only allowed to
be a class, a union of classes, and Any. This pull request amends
that sentence to clarify X may also be a typevar (or a union involving
classes, Any, and TypeVars).
(cherry picked from commit 130717f)

Co-authored-by: Michael Lee <michael.lee.0x2a@gmail.com>
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@Michael0x2a @miss-islington
Michael0x2a authored and miss-islington committed Sep 26, 2018
commit 6a01065f920e21d44dbefa7f17ec9cc295c0625b
9 changes: 6 additions & 3 deletions Doc/library/typing.rst
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Expand Up @@ -169,6 +169,8 @@ It is possible to declare the return type of a callable without specifying
the call signature by substituting a literal ellipsis
for the list of arguments in the type hint: ``Callable[..., ReturnType]``.

.. _generics:

Generics
--------

Expand All @@ -183,7 +185,7 @@ subscription to denote expected types for container elements.
def notify_by_email(employees: Sequence[Employee],
overrides: Mapping[str, str]) -> None: ...

Generics can be parametrized by using a new factory available in typing
Generics can be parameterized by using a new factory available in typing
called :class:`TypeVar`.

::
Expand Down Expand Up @@ -488,8 +490,9 @@ The module defines the following classes, functions and decorators:
required to handle this particular case may change in future revisions of
:pep:`484`.

The only legal parameters for :class:`Type` are classes, unions of classes, and
:data:`Any`. For example::
The only legal parameters for :class:`Type` are classes, :data:`Any`,
:ref:`type variables <generics>`, and unions of any of these types.
For example::

def new_non_team_user(user_class: Type[Union[BaseUser, ProUser]]): ...

Expand Down