python multiprocessing脚本不会退出

Question

我正在尝试使python2.7多处理模块更加舒适一些。 因此，我编写了一个小脚本，该脚本以文件名和所需的进程数作为输入，然后启动多个进程以将函数应用于队列中的每个文件名。 看起来像这样：

import multiprocessing, argparse, sys
from argparse import RawTextHelpFormatter

def parse_arguments():
    descr='%r\n\nTest different functions of multiprocessing module\n%r' % ('_'*80, '_'*80)
    parser=argparse.ArgumentParser(description=descr.replace("'", ""), formatter_class=RawTextHelpFormatter)
    parser.add_argument('-f', '--files', help='list of filenames', required=True, nargs='+')
    parser.add_argument('-p', '--processes', help='number of processes for script', default=1, type=int)
    args=parser.parse_args()
    return args 

def print_names(name):
    print name


###MAIN###

if __name__=='__main__':
    args=parse_arguments()
    q=multiprocessing.Queue()
    procs=args.processes
    proc_num=0
    for name in args.files:
        q.put(name)
    while q.qsize()!=0:
        for x in xrange(procs):
            proc_num+=1
            file_name=q.get()
            print 'Starting process %d' % proc_num
            p=multiprocessing.Process(target=print_names, args=(file_name,))
            p.start()
            p.join()
            print 'Process %d finished' % proc_num

该脚本可以正常工作，并且每当一个旧进程完成时就启动一个新进程（我认为这是这样吗？），直到队列中的所有对象都用完为止。 但是，该脚本不会在完成队列后退出，而是处于空闲状态，我必须使用Ctrl+C将其杀死。 这里有什么问题？

感谢您的回答！

Answer 1

似乎您在这里混了一些东西。 您生成一个流程，让它完成其工作，然后等待其退出，然后在下一次迭代中开始一个新流程。 使用这种方法，您会陷入顺序处理中，这里没有执行实际的多重处理。

也许您想以此为起点：

import sys
import os
import time
import multiprocessing as mp

def work_work(q):
    # Draw work from the queue
    item = q.get()
    while item:
        # Print own process id and the item drawn from the queue
        print(os.getpid(), item)
        # Sleep is only for demonstration here. Usually, you 
        # do not want to use this! In this case, it gives the processes
        # the chance to "work" in parallel, otherwise one process
        # would have finished the entire queue before a second one
        # could be spawned, because this work is quickly done.
        time.sleep(0.1)
        # Draw new work
        item = q.get()

if __name__=='__main__':
    nproc = 2  # Number of processes to be used
    procs = [] # List to keep track of all processes

    work = [chr(i + 65) for i in range(5)]
    q = mp.Queue() # Create a queue...
    for w in work:
        q.put(w) # ...and fill it with some work.

    for _ in range(nproc):
        # Spawn new processes and pass each of them a reference
        # to the queue where they can pull their work from.
        procs.append(mp.Process(target=work_work, args=(q,)))
        # Start the process just created.
        procs[-1].start()

    for p in procs:
        # Wait for all processes to finish their work. They only
        # exit once the queue is empty.
        p.join()