I need to check if object is descendant of typing.Literal, I have annotation like this:
GameState: Literal['start', 'stop']
And I need to check GameState
annotation type:
def parse_values(ann)
if isinstance(ann, str):
# do sth
if isinstance(ann, int):
# do sth
if isinstance(ann, Literal):
# do sth
But it causes error, so I swapped the last one to:
if type(ann) == Literal:
# do sth
But it never returns True, so anyone knows a workaround for this?
typing.get_origin(tp)
is the proper way
It was implemented in Python 3.8 (Same as typing.Literal
)
The docstring is thoroughly instructive:
def get_origin(tp):
"""Get the unsubscripted version of a type.
This supports generic types, Callable, Tuple, Union, Literal, Final, ClassVar
and Annotated. Return None for unsupported types. Examples::
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
"""
In your use case it would be:
from typing import Literal, get_origin
def parse_values(ann):
if isinstance(ann, str):
return "str"
elif isinstance(ann, int):
return "int"
elif get_origin(ann) is Literal:
return "Literal"
assert parse_values("foo") == "str"
assert parse_values(5) == "int"
assert parse_values(Literal["bar", 6]) == "Literal"