Core Python Programming (2nd Edition)

18 def writer(queue, loops):
19 for i in range(loops):
20 writeQ(queue)
21 sleep(randint(1, 3))
22
23 def reader(queue, loops):
24 for i in range(loops):
25 readQ(queue)
26 sleep(randint(2, 5))
27
28 funcs = [writer, reader]
29 nfuncs = range(len(funcs))
30
31 def main():
32 nloops = randint(2, 5)
33 q = Queue(32)
34
35 threads = []
36 for i in nfuncs:
37 t = MyThread(funcs[i], (q, nloops),
38 funcs[i].__name__)
39 threads.append(t)
40
41 for i in nfuncs:
42 threads[i].start()
43
44 for i in nfuncs:
45 threads[i].join()
46
47 print 'all DONE'
48
49 if __name__ == '__main__':
50 main()
Here is the output from one execution of this script:
$ prodcons.py
starting writer at: Sun Jun 18 20:27:07 2006
producing object for Q... size now 1
starting reader at: Sun Jun 18 20:27:07 2006
consumed object from Q... size now 0
producing object for Q... size now 1
consumed object from Q... size now 0
producing object for Q... size now 1
producing object for Q... size now 2
producing object for Q... size now 3
consumed object from Q... size now 2
consumed object from Q... size now 1
writer finished at: Sun Jun 18 20:27:17 2006
consumed object from Q... size now 0
reader finished at: Sun Jun 18 20:27:25 2006
all DONE
As you can see, the producer and consumer do not necessarily alternate in execution. (Thank goodness