How to Share a Result Queue Between Multiple Processes in Python?

How to Share a Result Queue Among Multiple Processes

When working with asynchronous worker processes using the multiprocessing module's apply_async() function, it's important to consider how to share a queue safely. The error "RuntimeError: Queue objects should only be shared between processes through inheritance" highlights the need to pass the queue in a way that prevents pickling/unpickling issues.

To resolve this, we can leverage the multiprocessing.Manager() class, which provides a way to manage objects and make them accessible to different workers.

<code class="python">import multiprocessing

def worker(name, que):
    que.put("%d is done" % name)

if __name__ == '__main__':
    pool = multiprocessing.Pool(processes=3)
    m = multiprocessing.Manager()
    q = m.Queue()
    workers = pool.apply_async(worker, (33, q))</code>

In this example, we create a Manager object (m) and use it to manage the queue (q). By doing so, we create a shared memory segment that allows multiple processes to access the queue safely, even in asynchronous scenarios.

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