'Acquire a multiprocessing.Lock in a with statement if non-blocking or with timeout

With a normal multiprocessing.Lock (or threading.Lock) you can simplify the following code:

lock = multiprocessing.Lock()

lock.acquire()

try:
    ...
finally:
    lock.release()

into:

with lock:
    ...

However, can I still use a context manager when I want to pass some arguments to lock.acquire(...), such as block= or timeout=? For example, I have code like this:

lock_success = lock.acquire(block=False)

if not lock_success:
    return

try:
    ...
finally:
    lock.release()

I don't see a way to pass this argument to the context manager (since it's in the acquire call and not the constructor).

(The idea is that the with-block would get skipped if the lock cannot be acquired.)

Analogously for threading.Lock which provides a similar API.

pythonmultithreadingmultiprocessingpython-multithreading


Solution 1:[1]

My suspicion is that this is not possible because of how context managers are designed in Python. What happens with a context manager (CM) is:

with CM:
    ...
  • The CM's __enter__ method is called
  • The block inside of with is run
  • The CM's __exit__ method is called

Thus there is no way to "skip" the inside of the with-block, so I guess this explains the design of the Lock class. Although there are some dark magic ways around that (which should be avoided).

Sources

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Source: Stack Overflow

Solution Source
Solution 1 xjcl

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