1  import time
       2  import random
       3  
       4  from multiprocessing import Process, Queue, current_process, freeze_support
       5  
       6  #
       7  # Function run by worker processes
       8  #
       9  
      10  def worker(input, output):
      11      for func, args in iter(input.get, 'STOP'):
      12          result = calculate(func, args)
      13          output.put(result)
      14  
      15  #
      16  # Function used to calculate result
      17  #
      18  
      19  def calculate(func, args):
      20      result = func(*args)
      21      return '%s says that %s%s = %s' % \
      22          (current_process().name, func.__name__, args, result)
      23  
      24  #
      25  # Functions referenced by tasks
      26  #
      27  
      28  def mul(a, b):
      29      time.sleep(0.5*random.random())
      30      return a * b
      31  
      32  def plus(a, b):
      33      time.sleep(0.5*random.random())
      34      return a + b
      35  
      36  #
      37  #
      38  #
      39  
      40  def test():
      41      NUMBER_OF_PROCESSES = 4
      42      TASKS1 = [(mul, (i, 7)) for i in range(20)]
      43      TASKS2 = [(plus, (i, 8)) for i in range(10)]
      44  
      45      # Create queues
      46      task_queue = Queue()
      47      done_queue = Queue()
      48  
      49      # Submit tasks
      50      for task in TASKS1:
      51          task_queue.put(task)
      52  
      53      # Start worker processes
      54      for i in range(NUMBER_OF_PROCESSES):
      55          Process(target=worker, args=(task_queue, done_queue)).start()
      56  
      57      # Get and print results
      58      print('Unordered results:')
      59      for i in range(len(TASKS1)):
      60          print('\t', done_queue.get())
      61  
      62      # Add more tasks using `put()`
      63      for task in TASKS2:
      64          task_queue.put(task)
      65  
      66      # Get and print some more results
      67      for i in range(len(TASKS2)):
      68          print('\t', done_queue.get())
      69  
      70      # Tell child processes to stop
      71      for i in range(NUMBER_OF_PROCESSES):
      72          task_queue.put('STOP')
      73  
      74  
      75  if __name__ == '__main__':
      76      freeze_support()
      77      test()