Let's say I have a function that accepts a Garthok
, an Iterable[Garthok]
, an Iterable[Iterable[Garthok]]
, etc.
def narfle_the_garthoks(arg):
if isinstance(arg, Iterable):
for value in arg:
narfle_the_garthoks(arg)
else:
arg.narfle()
Is there any way to specify a type hint for arg that indicates that it accepts any level of Iterable
s of Garthok
s? I suspect not, but thought I'd check if I'm missing something.
As a workaround, I'm just specifying a few levels deep, and then ending with Iterable[Any]
.
Union[Garthok,
Iterable[Union[Garthok,
Iterable[Union[Garthok,
Iterable[Union[Garthok, Iterable[Any]]]]]]]]
You can specify recursive types in the typing language by using type aliases and forward reference strings,
Garthoks = Union[Garthok, Iterable['Garthoks']]
Mypy supports recursive types by default since v0.990.
Update 2020/9/14: Microsoft announces support for recursive types in Pyright/Pylance.
Some types of forward references are handled by PEP 0563. You can use them starting from Python 3.7 by doing
from __future__ import annotations
– Konstantin
As of Python 3.12, __future__.annotations
/stringifying is not necessary if the type is defined using a type
statement:
type Garthoks = Garthok | Iterable[Garthoks]]