Multiprocessing Queue in Python

Question

I\'m trying to use a queue with the multiprocessing library in Python. After executing the code below (the print statements work), but the processes do not quit after I call

Answer 1

Your workers need a sentinel to terminate, or they will just sit on the blocking reads. Note that using sleep on the Q instead of join on the P lets you display status information etc.
My preferred template is:

def worker(q,nameStr):
  print 'Worker %s started' %nameStr
  while True:
     item = q.get()
     if item is None: # detect sentinel
       break
     print '%s processed %s' % (nameStr,item) # do something useful
     q.task_done()
  print 'Worker %s Finished' % nameStr
  q.task_done()

q = multiprocessing.JoinableQueue()
procs = []
for i in range(num_procs):
  nameStr = 'Worker_'+str(i)
  p = multiprocessing.Process(target=worker, args=(q,nameStr))
  p.daemon = True
  p.start()
  procs.append(p)

source = ['hi','there','how','are','you','doing']
for item in source:
  q.put(item)

for i in range(num_procs):
  q.put(None) # send termination sentinel, one for each process

while not q.empty(): # wait for processing to finish
  sleep(1)   # manage timeouts and status updates etc.