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Union of ParamSpec? #17481
Description
Feature
Currently it's possible to concatenate a type to a paramspec to get a new paramspec.
I think I may need the ability to concatenate two paramspecs, like:
P = ParamSpec('P')
Q = ParamSpec('Q')
R = TypeVar("R")
Callable[Concatenate[P, Q], R]
Pitch
I'm trying to describe partial-like functions, I spotted #16939 which solves if for functools.partial (which is good) but still not giving a way to describe other partial-like functions.
Currently I can successfully describe the "removal" of one or multiple parameters:
from collections.abc import Callable
from typing import Concatenate, Generic, ParamSpec, TypeVar
P = ParamSpec('P')
Q = ParamSpec('Q')
S = TypeVar('S')
T = TypeVar('T')
U = TypeVar('U')
def substract_one_parameter(given: T, func: Callable[Concatenate[T, P], U]) -> Callable[P, U]:
def inner(*args: P.args, **kwargs: P.kwargs) -> U:
return func(given, *args, **kwargs)
return inner
def substract_two_parameters(first: S, second: T, func: Callable[Concatenate[S, T, P], U]) -> Callable[P, U]:
def inner(*args: P.args, **kwargs: P.kwargs) -> U:
return func(first, second, *args, **kwargs)
return inner
def int_int_int(a: int, b: int) -> int:
return a + b
c = substract_one_parameter(1, int_int_int)
reveal_type(c) # def (b: builtins.int) -> builtins.int
print(c(2))
d = substract_two_parameters(1, 2, int_int_int)
reveal_type(d) # def () -> builtins.int
print(d())But what I think I need is:
# P are the "removed" parameters
# Q are the "kept" parameters
def substract_n_parameters(func: Callable[Concatenate[P, Q], U], *outer_args: P.args, **outer_kwargs: P.kwargs) -> Callable[Q, U]:
def inner(*args: Q.args, **kwargs: Q.kwargs) -> U:
return func(*outer_args, *args, **outer_kwargs, **kwargs)
return innerI feel that would cleanly express the "removal" of P from [P, Q], without the need to introduce a new function like Difference[P, Q].
I feel like this could also be used for the real functools.partial, maybe simplifying the current (working, yeah) implementation.
Activity
mantasu commented on Jul 24, 2024
Indeed, it would be great to have this feature:
Currently, as in PEP 612, Concatenate only allows a single ParamSpec.