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gh-91243: Add typing.Required and NotRequired (PEP 655) (GH-32419)

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I talked to @davidfstr and I offered to implement the runtime part of PEP 655
to make sure we can get it in before the feature freeze. We're going to defer
the documentation to a separate PR, because it can wait until after the feature
freeze.

The runtime implementation conveniently already exists in typing-extensions,
so I largely copied that.

Co-authored-by: David Foster <david@dafoster.net>
This commit is contained in:
Jelle Zijlstra 2022-04-12 12:31:02 -07:00 • committed by GitHub
parent 474fdbe9e4
commit ac6c3de03c
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4 changed files with 241 additions and 6 deletions
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63
Lib/typing.py
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@ -132,9 +132,11 @@ __all__ = [
'no_type_check',
'no_type_check_decorator',
'NoReturn',
'NotRequired',
'overload',
'ParamSpecArgs',
'ParamSpecKwargs',
'Required',
'reveal_type',
'runtime_checkable',
'Self',
@ -2262,6 +2264,8 @@ def _strip_annotations(t):
"""
if isinstance(t, _AnnotatedAlias):
return _strip_annotations(t.__origin__)
if hasattr(t, "__origin__") and t.__origin__ in (Required, NotRequired):
return _strip_annotations(t.__args__[0])
if isinstance(t, _GenericAlias):
stripped_args = tuple(_strip_annotations(a) for a in t.__args__)
if stripped_args == t.__args__:
@ -2786,10 +2790,22 @@ class _TypedDictMeta(type):
optional_keys.update(base.__dict__.get('__optional_keys__', ()))
annotations.update(own_annotations)
if total:
required_keys.update(own_annotation_keys)
else:
optional_keys.update(own_annotation_keys)
for annotation_key, annotation_type in own_annotations.items():
annotation_origin = get_origin(annotation_type)
if annotation_origin is Annotated:
annotation_args = get_args(annotation_type)
if annotation_args:
annotation_type = annotation_args[0]
annotation_origin = get_origin(annotation_type)
if annotation_origin is Required:
required_keys.add(annotation_key)
elif annotation_origin is NotRequired:
optional_keys.add(annotation_key)
elif total:
required_keys.add(annotation_key)
else:
optional_keys.add(annotation_key)
tp_dict.__annotations__ = annotations
tp_dict.__required_keys__ = frozenset(required_keys)
@ -2874,6 +2890,45 @@ _TypedDict = type.__new__(_TypedDictMeta, 'TypedDict', (), {})
TypedDict.__mro_entries__ = lambda bases: (_TypedDict,)
@_SpecialForm
def Required(self, parameters):
"""A special typing construct to mark a key of a total=False TypedDict
as required. For example:
class Movie(TypedDict, total=False):
title: Required[str]
year: int
m = Movie(
title='The Matrix', # typechecker error if key is omitted
year=1999,
)
There is no runtime checking that a required key is actually provided
when instantiating a related TypedDict.
"""
item = _type_check(parameters, f'{self._name} accepts only a single type.')
return _GenericAlias(self, (item,))
@_SpecialForm
def NotRequired(self, parameters):
"""A special typing construct to mark a key of a TypedDict as
potentially missing. For example:
class Movie(TypedDict):
title: str
year: NotRequired[int]
m = Movie(
title='The Matrix', # typechecker error if key is omitted
year=1999,
)
"""
item = _type_check(parameters, f'{self._name} accepts only a single type.')
return _GenericAlias(self, (item,))
class NewType:
"""NewType creates simple unique types with almost zero
runtime overhead. NewType(name, tp) is considered a subtype of tp