1 from multiprocessing import Pool, cpu_count
   2 import time
   3 import random
   4 
   5 def f(x):
   6     sec = random.choice([1,2,3])
   7     print 'before ', x, 'wait %s sec' % sec
   8     time.sleep(sec)
   9     print 'after ', x
  10     return x*x
  11 
  12 def aa():
  13     i = 0
  14     while i < 20:
  15         yield i
  16         i += 1
  17 
  18 if __name__ == '__main__':
  19     pool = Pool(processes=4)
  20     for each in pool.imap(f, aa()):
  21         print each