Shareable Lock

shareable_lock is a lock implementation that uses file locking underneath that can be shared across Python processes. Available locks from multiprocessing and threading don't allow for sharing instances for the same locks across Python processes. With shareable_lock's ShareableLock, a lock for the same resource can be instantiated across different Python processes by creating an instance of the ShareableLock with the same locking file.

Installing

Use uv to install the shareable_lock to your project.

uv pip install shareable_lock

Creating the Lock instance

To create an instance of the lock, you can provide the path for the file associated with the resource being locked. Using the same file name across different processes implies locking the same resource. The create argument should be set to True for one of these processes to create the file used for locking and all other processes can create an instance of the lock for the same resource with create = False.

from shareable_lock import ShareableLock

lock = ShareableLock(fname = "lock.lock", create = True)

Acquiring the Lock

To acquire the lock, create the instance of the ShareableLock and use the acquire method. This uses the fcntl.flock internally to get a fcntl.LOCK_EX type lock on the file. If fcntl.flock fails, an IOError is raised.

from shareable_lock import ShareableLock

lock = ShareableLock()
if lock.acquire(): 
    print("Lock acquired.")

A timeout can also be set to interrupt the acquire method after a give number of seconds pass.

from shareable_lock import ShareableLock

lock = ShareableLock()
if lock.acquire(): 
    print("Lock acquired.")
else:
    print("Acquire method timedout.")

Releasing the Lock

To release the lock, create the instance of the ShareableLock and use the release method. This uses the fcntl.floc(self.fd, fcntl.LOCK_UN) to release the fcntl.LOCK_EX on the file. If fcntl.flock fails, an IOError is raised.

from shareable_lock import ShareableLock

lock = ShareableLock()
lock.acquire()

lock.release()

Trying to release an unacquired lock will raise an assertion error.

from shareable_lock import ShareableLock

lock = ShareableLock()
lock.release()

Deleting the Lock

The lock should be deleted once it is no longer being used by a process.

from shareable_lock import ShareableLock

lock = ShareableLock()
lock.delete()

The process that created the file being used by the ShareableLock should call delete with unlink = True. This will delete the file in addition to closing it.

from shareable_lock import ShareableLock

lock = ShareableLock(create = True)
lock.delete(unlink = True)