The following example code works at runtime, but is not accepted by mypy --strict:
from typing import Any, Callable, TypeVar
TypeT = TypeVar('TypeT')
def log_call(msg: str) -> Callable[..., TypeT]:
def do_call(func: Callable[..., TypeT], *args: Any, **kwargs: Any) -> TypeT:
print(msg)
return func(*args, **kwargs)
return do_call
def double(val: int) -> int:
return 2 * val
def plus(a: int, b: int) -> int:
return a + b
def plus_plus(a: int, b: int, c: int) -> int:
return a + b + c
result_1 = log_call('hi')(double, 1)
result_2 = log_call('hi')(plus, 2, 3)
result_3 = log_call('hi')(plus_plus, 2, 3, 4)
result_4 = log_call('hi')(double, val=1)
print(result_1)
print(result_2)
print(result_3)
print(result_4)
mypy output:
test.py:26: error: Need type annotation for 'result_1'
test.py:27: error: Need type annotation for 'result_2'
test.py:28: error: Need type annotation for 'result_3'
test.py:30: error: Need type annotation for 'result_4'
test.py:32: error: Cannot determine type of 'result_1'
test.py:33: error: Cannot determine type of 'result_2'
test.py:34: error: Cannot determine type of 'result_3'
test.py:35: error: Cannot determine type of 'result_4'
Now instead of adding the type annotations to the result* variables, I would like to adjust the type annotation of the function, so the others can be deduced. This is my attempt:
from typing import Any, Callable, TypeVar
TypeT = TypeVar('TypeT')
def log_call(msg: str) -> Callable[[Callable[..., TypeT], Any, Any], TypeT]:
def do_call(func: Callable[..., TypeT], *args: Any, **kwargs: Any) -> TypeT:
print(msg)
return func(*args, **kwargs)
return do_call
def double(val: int) -> int:
return 2 * val
def plus(a: int, b: int) -> int:
return a + b
def plus_plus(a: int, b: int, c: int) -> int:
return a + b + c
result_1 = log_call('hi')(double, 1)
result_2 = log_call('hi')(plus, 2, 3)
result_3 = log_call('hi')(plus_plus, 2, 3, 4)
result_4 = log_call('hi')(double, val=1)
print(result_1)
print(result_2)
print(result_3)
print(result_4)
However now the number of parameters does not fit any more:
test.py:26: error: Too few arguments
test.py:28: error: Too many arguments
test.py:30: error: Unexpected keyword argument "val"
I guess I'm looking for something like
def log_call(msg: str) -> Callable[[Callable[..., TypeT], ...], TypeT]:
But this syntax is not legal.
Is there a way I could solve this?