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typing-utils

Backport Python3.8+ typing utils & issubtype & more

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Python 3.6 Python 3.7 Python 3.8 Python 3.9

Install

pip install typing_utils

API

issubtype

Check that the left argument is a subtype of the right.

For unions, check if the type arguments of the left is a subset of the right. Also works for nested types including ForwardRefs.

Examples:

from typing_utils import issubtype

issubtype(typing.List, typing.Any) == True
issubtype(list, list) == True
issubtype(list, typing.List) == True
issubtype(list, typing.Sequence) == True
issubtype(typing.List[int], list) == True
issubtype(typing.List[typing.List], list) == True
issubtype(list, typing.List[int]) == False
issubtype(list, typing.Union[typing.Tuple, typing.Set]) == False
issubtype(typing.List[typing.List], typing.List[typing.Sequence]) == True
JSON = typing.Union[
    int, float, bool, str, None, typing.Sequence["JSON"],
    typing.Mapping[str, "JSON"]
]
issubtype(str, JSON, forward_refs={'JSON': JSON}) == True
issubtype(typing.Dict[str, str], JSON, forward_refs={'JSON': JSON}) == True
issubtype(typing.Dict[str, bytes], JSON, forward_refs={'JSON': JSON}) == False

get_origin

Get the unsubscripted version of a type.

This supports generic types, Callable, Tuple, Union, Literal, Final and ClassVar. Return None for unsupported types.

Examples:

from typing_utils import get_origin

get_origin(Literal[42]) is Literal
get_origin(int) is None
get_origin(ClassVar[int]) is ClassVar
get_origin(Generic) is Generic
get_origin(Generic[T]) is Generic
get_origin(Union[T, int]) is Union
get_origin(List[Tuple[T, T]][int]) == list

get_args

Get type arguments with all substitutions performed.

For unions, basic simplifications used by Union constructor are performed.

Examples:

from typing_utils import get_args

get_args(Dict[str, int]) == (str, int)
get_args(int) == ()
get_args(Union[int, Union[T, int], str][int]) == (int, str)
get_args(Union[int, Tuple[T, int]][str]) == (int, Tuple[str, int])
get_args(Callable[[], T][int]) == ([], int)

get_type_hints

Return type hints for an object.

This is often the same as obj.annotations, but it handles forward references encoded as string literals, and if necessary adds Optional[t] if a default value equal to None is set.

The argument may be a module, class, method, or function. The annotations are returned as a dictionary. For classes, annotations include also inherited members.

TypeError is raised if the argument is not of a type that can contain annotations, and an empty dictionary is returned if no annotations are present.

BEWARE -- the behavior of globalns and localns is counterintuitive (unless you are familiar with how eval() and exec() work). The search order is locals first, then globals.