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cache_args
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| # License: MIT | |
| # Copyright (c) David D. Dorfman 2022 | |
| """ | |
| Cache function arguments from callables on first invocation | |
| """ | |
| from functools import partial, wraps | |
| from typing import Any, Callable, Optional, ParamSpec, TypeVar | |
| P = ParamSpec('P') | |
| R = TypeVar('R') | |
| def cache_args(*positional_gets: Callable[[], Any], **kwargs_gets: Callable[[], Any]): | |
| """ | |
| Compute values for the specified args on first invocation of the function and cache them for future calls. | |
| Cached positional args cannot be overridden. Caching keyword args is akin to caching default values. | |
| """ | |
| def decorate(func: Callable) -> Callable: | |
| partial_func: Optional[partial[R]] = None | |
| def wrapper(*args, **kwargs) -> R: | |
| nonlocal partial_func | |
| if partial_func is None: | |
| partial_args = [get_arg() for get_arg in positional_gets] | |
| partial_kwargs = {kwarg: get_kwargs() for kwarg, get_kwargs in kwargs_gets.items()} | |
| partial_func = partial(func, *partial_args, **partial_kwargs) | |
| partial_func = wraps(func)(partial_func) | |
| return partial_func(*args, **kwargs) | |
| return wrapper | |
| return decorate | |
| # Example: | |
| import platform | |
| import distro | |
| @cache_args(platform.machine, c=distro.id) | |
| def f(a, b, *, c, d): | |
| print(f'{a=} {b=} {c=} {d=}') | |
| f('xyz', d='abc') | |
| # a='x86_64' b='xyz' c='darwin' d='abc' |
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