multiprocessing - Process synchronization in Python -

i try synchronize multiple processes using semaphores. thought instead of creating function each process, might possible in more generic way, single function , arguments dependencies:

import multiprocessing multiprocessing import *  class worker:     def __init__(self, size):         self._semaphores = [semaphore(0)]*(size + 1)      def run(self, name, acquire, release):         in acquire:             self._semaphores[i].acquire()              print('running', name)          in release:             self._semaphores[i].release() 

in case i've got 5 processes. first starts first, second , third after first, fourth after second , third, , fifth after fourth.

if __name__ == '__main__':     worker = worker(5)     process(target=worker.run, args=('5', [5], [])).start()     process(target=worker.run, args=('4', [4,4], [5])).start()     process(target=worker.run, args=('3', [3], [4])).start()     process(target=worker.run, args=('2', [2], [4])).start()     process(target=worker.run, args=('1', [], [2,3])).start() 

the expected output be:

running 1 running 2 running 3 running 4 running 5 

but synchronization doesn't work expected. execution random including deadlocks. why that?

[semaphore(0)]*(size + 1) creates list size + 1 references single semaphore object. need make different instances of class:

self._semaphores = [semaphore(0) _ in range(size + 1)]