Sharing Locks Among Python Processes

When attempting to use a lock between multiple processes, you may encounter the error, "Lock objects should only be shared between processes through inheritance."

To resolve this, there are two main approaches:

Using a Manager

This approach involves creating a Manager object and passing a Manager.Lock():

from multiprocessing import Manager
...
m = Manager()
l = m.Lock()

Using a Manager, however, introduces the need for an additional process to host the Manager server and communicates through IPC.

Passing the Lock at Pool Creation

An alternative method is to pass the regular multiprocessing.Lock() at Pool creation time using the initializer keyword argument:

def init(l):
    global lock
    lock = l

l = multiprocessing.Lock()
pool = multiprocessing.Pool(initializer=init, initargs=(l,))

This method makes the lock instance global in all the child workers. Note that this approach eliminates the need for the partial function.

By employing one of these techniques, you can effectively share locks between Python processes, allowing for coordinated access to shared resources.