Semaphore's value argument

[multimeric]

Currently we assume that the semaphore's value must be an integer:

typeshed/stdlib/asyncio/locks.pyi

Lines 88 to 93 in 1af9de6

	_value: int
	_waiters: deque[Future[Any]] | None
	if sys.version_info >= (3, 10):
	def __init__(self, value: int = 1) -> None: ...
	else:
	def __init__(self, value: int = 1, *, loop: AbstractEventLoop | None = None) -> None: ...

Generally this is correct, but I had a use case where I wanted to disable the semaphore without restructuring my code, so I used float("inf") as the value to ensure that it never unlocks. This works perfectly fine, because the only operations that value needs to support are:

• Adding 1
• Subtracting 1
• Comparing to 0

The infinity float value does all of these fine. So I therefore wonder if we should make this type be int | Literal[math.inf]? I agree that general floats are not a good idea because they will get below 0 without triggering the wait.

[JelleZijlstra]

I therefore wonder if we should make this type be int | Literal[math.inf]?

Unfortunately the type system does not allow this; float is not an allowed literal type. Cross-linking python/typing#1160.

[multimeric]

Wow, I didn't know that. Dare I suggest int | float then?

[srittau]

I'm honestly wary to allow arbitrary floats here as using them could lead to bugs due to floating point math. I would suggest to use a big int instead, e.g. 2**64-1.