Python locks that go away when process dies

Question

Is there any locking interface for Python that automatically breaks the lock when the process dies? I was under the impression that sysv ipc allows for that, but I'm still trying to figure out the details.

What I expect from the interface:

• lock / release functions
• working between different processes on Linux
• automatic unlock when the process holding the lock dies
• forced lock breaking on timeout (not necessary)

Answer 1

You could apply locks to a file using fcntl.lockf or fcntl.flock . That seems to meet all your criteria. Or do you need something that doesn't require a system call every time you want to lock or unlock?

Answer 2

I usually use a try ... finally block to release a lock. eg

try:
    #do stuff
except Exception:
    pass
finally:
    #release lock

Answer 3

You could try the Lock objects in the built in multiprocessing package. I'm not sure whether the lock will automatically unlock when a process is garbage collected, but you could always subclass multiprocessing.Process like this:

class MyProc(multiprocessing.Process):
    def __init__(self):
        self.ipc_lock = multiprocessing.Lock()
        # ...
        return
    def __del__(self):
        self.ipc_lock.release()
        return

if you need to unlock if an exception is fired then put that in the (overridden) run method.