mypy

error

$ mypy test.py
test.py:71: error: List comprehension has incompatible type List[Callable[[List[str]], List[str]]]; expected List[Callable[[Arg(List[str], 'names')], List[str]]]

test.py

from functools import reduce
from itertools import combinations
from typing import List, Callable, Sequence, TypeVar

X = TypeVar("X")
Y = TypeVar("Y")
Z = TypeVar("Z")


def compose(f: Callable[[Y], Z], g: Callable[[X], Y]) -> Callable[[X], Z]:
    def composed_function(arg: X) -> Z:
        return f(g(arg))

    composed_function.__name__ = composed_function.__qualname__ = "_".join(
        (f.__name__, g.__name__)
    )
    return composed_function


Names = List[str]


def remove_none(names: Names) -> Names:
    return names


def remove_nonblank(names: Names) -> Names:
    return list(filter(None, names))


def remove_short(names: Names) -> Names:
    return [name for name in names if len(name) > 2]


Refiners = Sequence[Callable[[Names], Names]]

UNIQUE_REFINERS: Refiners = [remove_short, remove_nonblank]

REFINERS: Refiners = [remove_none] + [
    reduce(compose, combination)
    for i in range(1, len(UNIQUE_REFINERS))
    for combination in combinations(UNIQUE_REFINERS, i)
]