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(4) for i in range(5): p.apply_async(long_time_task, args=(i,)) print('Waiting for all subprocesses done...') p.close() p.join() print('All subprocesses done.') Parent process 7904. Waiting for all subprocesses done... None Run task 0 (9196)... Run task 1 (8076)... Run task 2 (11612)... Run task 3 (6164)... Task 1 runs 1.84 seconds. Run task 4 (8076)... Task 0 runs 2.12 seconds. Task 4 runs 0.35 seconds. Task 3 runs 2.57 seconds. Task 2 runs 2.93 seconds. All subprocesses done.
进程是在for循环创建的,只是一次只能运行4个,要等别的进程运行完毕,才能运行4。
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