from multiprocessing import Pool
import os, time, random

def long_time_task(name):
    print('Run task %s (%s)...' % (name, os.getpid()))
    start = time.time()
    time.sleep(random.random() * 3)
    end = time.time()
    print('Task %s runs %0.2f seconds.' % (name, (end - start)))

if __name__=='__main__':
    print('Parent process %s.' % os.getpid())
    p = Pool(9)
    res=[]
    for i in range(10):
        p.apply_async(long_time_task, (i,))
    print('Waiting for all subprocesses done...')
    p.close()
    p.join()
    print('All subprocesses done.')

执行结果和例子的不一样。是怎么回事？例子结果是：

Parent process 669.
Waiting for all subprocesses done...
Run task 0 (671)...
Run task 1 (672)...
Run task 2 (673)...
Run task 3 (674)...
Task 2 runs 0.14 seconds.
Run task 4 (673)...
Task 1 runs 0.27 seconds.
Task 3 runs 0.86 seconds.
Task 0 runs 1.41 seconds.
Task 4 runs 1.91 seconds.
All subprocesses done.

我的是这样的

Parent process 12044.
Waiting for all subprocesses done...
All subprocesses done.