python multiprocessing example with return values

mp_example.py

#!/usr/bin/env python3

import multiprocessing as mp

SENTINEL = None

dat = range(10)
rets = []

def function( *args ):
    a = args[0]
    return a

def worker( qIn, qOut ):
    for f in iter( qIn.get, SENTINEL ):
        res = function( f )
        qOut.put( res )

qIn = mp.Queue() # to hold the inputs
qOut = mp.Queue() # to hold the outputs

procs = [ mp.Process( target = worker, args = [qIn, qOut] ) for i in range( mp.cpu_count() ) ]
for p in procs:
    p.start()

for d in dat:
    qIn.put( d )

for p in procs:
    qIn.put( SENTINEL )
    
for p in procs:
    p.join()

# put qOut back into a list
qlist = []
while qOut.qsize() > 0:
    qlist.append( qOut.get() )