Python 3.10+typingterm

typing.ParamSpec

generics and parameters

A parameter specification variable: it captures a call signature (positional and keyword) to type decorators and wrappers (Python 3.10+).

Syntax

P = typing.ParamSpec('P')

Use it for a decorator/wrapper that must keep the wrapped function's signature: without ParamSpec you fall back to Callable[..., T], lose the parameter types, and the checker stops catching bad calls. It pairs with Callable and Concatenate and needs Python 3.10+ (typing_extensions on older versions).

Examples

from typing import ParamSpec
P = ParamSpec('P')
print(P.__name__)   # → P
print(P.args)   # → P.args
print(P.kwargs)   # → P.kwargs
def wrapper(*args: P.args, **kwargs: P.kwargs) -> None: pass
print(wrapper.__annotations__['args'])   # → P.args

See also

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