The purpose of the pool in python multiprocessing

Question

I'm having difficulty understanding the purpose of the pool in Python's multiprocessing module.

I know what this code is doing:

import multiprocessing

def worker():
    """worker function"""
    print 'Worker'
    return

if __name__ == '__main__':
    jobs = []
    for i in range(5):
        p = multiprocessing.Process(target=worker)
        jobs.append(p)
        p.start()

So my question is, in what type of situation would a pool be used?

Answer 1

Pool objects are useful when you want to be able to submit more tasks to sub-processes, but you don't want to handle all the organization of these tasks(ie how many processes should be spawned to handle them; which task go to which process etc.) and you care only for the result value, and not any other kind of synchronisation etc. You don't want to have the control over the sub-process computation but simply the result.

On the other hand Process is used when you want to execute a specific action, and you need control over the sub-process, not only on the result of its computation.