Twisted's DeferredQueue

import itertools
from twisted.internet import defer
from twisted.internet import reactor
from twisted.internet import task

FREQUENCY = 10

def startProducing(q):
   """Put an incrementing number in the queue every 1/FREQUENCY
   seconds.
   """
   counter = itertools.count()
   def produce():
       q.put(counter.next())
   task.LoopingCall(produce).start(1.0/FREQUENCY)

def startConsuming(q):
   """Consume an object from the queue and print it.
   """
   def consumer(o):
       print o
       q.get().addCallback(consumer)
   q.get().addCallback(consumer)

q = defer.DeferredQueue()
startProducing(q)
startConsuming(q)

reactor.run()