Lock vs BoundedSemaphore(1) vs Semaphore(0) /u/AntFun3543 Python Education

When it comes to multiprocessing.Event objects, my understanding is that a Semaphore(0) enables non-blocking queries to the underlying state via its internal counter. This seems to distinguish it from a Lock, which is naturally exclusive and lacks a counter, making it only queryable in a blocking manner.

I’m also under the impression (with some uncertainty!) that a BoundedSemaphore(1) shares similarities with a Semaphore(0) in how it might function as a synchronization primitive for binary states.

Given this, why wouldn’t we prefer a standard Lock API that supports both blocking and non-blocking functionality directly? It seems this could simplify some of these use cases and reduce reliance on “engineered” configurations of Semaphore.

If I’m misunderstanding the nuanced differences between BoundedSemaphore(1) and Semaphore(0) or overlooking something in the documentation, I’d greatly appreciate clarification! I’m happy to provide additional examples or context if needed.

Thank you in advance!

EDIT:
Here’s the multiprocessing.Event code for context:

# # Event # class Event(object): def __init__(self, *, ctx): self._cond = ctx.Condition(ctx.Lock()) self._flag = ctx.Semaphore(0) def is_set(self): with self._cond: if self._flag.acquire(False): self._flag.release() return True return False def set(self): with self._cond: self._flag.acquire(False) self._flag.release() self._cond.notify_all() def clear(self): with self._cond: self._flag.acquire(False) def wait(self, timeout=None): with self._cond: if self._flag.acquire(False): self._flag.release() else: self._cond.wait(timeout) if self._flag.acquire(False): self._flag.release() return True return False def __repr__(self) -> str: set_status = 'set' if self.is_set() else 'unset' return f"<{type(self).__qualname__} at {id(self):#x} {set_status}>" 

When it comes to multiprocessing.Event objects, my understanding is that a Semaphore(0) enables non-blocking queries to the underlying state via its internal counter. This seems to distinguish it from a Lock, which is naturally exclusive and lacks a counter, making it only queryable in a blocking manner.

I’m also under the impression (with some uncertainty!) that a BoundedSemaphore(1) shares similarities with a Semaphore(0) in how it might function as a synchronization primitive for binary states.

Given this, why wouldn’t we prefer a standard Lock API that supports both blocking and non-blocking functionality directly? It seems this could simplify some of these use cases and reduce reliance on “engineered” configurations of Semaphore.

If I’m misunderstanding the nuanced differences between BoundedSemaphore(1) and Semaphore(0) or overlooking something in the documentation, I’d greatly appreciate clarification! I’m happy to provide additional examples or context if needed.

Thank you in advance!

EDIT:
Here’s the multiprocessing.Event code for context:

# # Event # class Event(object): def __init__(self, *, ctx): self._cond = ctx.Condition(ctx.Lock()) self._flag = ctx.Semaphore(0) def is_set(self): with self._cond: if self._flag.acquire(False): self._flag.release() return True return False def set(self): with self._cond: self._flag.acquire(False) self._flag.release() self._cond.notify_all() def clear(self): with self._cond: self._flag.acquire(False) def wait(self, timeout=None): with self._cond: if self._flag.acquire(False): self._flag.release() else: self._cond.wait(timeout) if self._flag.acquire(False): self._flag.release() return True return False def __repr__(self) -> str: set_status = 'set' if self.is_set() else 'unset' return f"<{type(self).__qualname__} at {id(self):#x} {set_status}>"