function with some of its argument values frozen

consider this coroutine function:

async def run_in_threadpool(func: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T:
    func = functools.partial(func, *args, **kwargs)
    return await anyio.to_thread.run_sync(func)

I actually got this coroutine function from starlette and based on my limited knowledge of asgi frameworks, this is a coroutine function that will run a sync callable func in a thread pool so it doesn't block or hog the event loop. in other words, if you for example create a sync endpoint, starlette does not have any problem handling it. it detects that the endpoint is not an async callable and then run it in a thread pool instead.

and what role dothfunctools.partial serve in this affair?

func = functools.partial(func, *args, **kwargs)`

this is a higher order function, in my environment configurations with pydantic settings blog, I used @lru_cache() to cache loaded env configs so i don’t keep reading from the env file every time. so these higher-order functions either take functions as input or return new ones.

what partial is doing here is creating a new callable, a partial object where the arguments we passed are already attached to it. when starlette calls it in run_sync, it doesn’t need to pass anything again, it just runs the function with those saved arguments.