python 多进程实例 进程间的通信

import httplib2from multiprocessing import Lock, Process, Queue, current_processdef worker(work_queue, done_queue):    try:        for url in iter(work_queue.get, 'STOP'):            status_code = print_site_status(url)            done_queue.put("%s - %s got %s." % (current_process().name, url, status_code))    except Exception, e:        done_queue.put("%s failed on %s with: %s" % (current_process().name, url, e))    return Truedef print_site_status(url):    http = httplib2.Http(timeout=10)    headers, content = http.request(url)    return headers.get('status', 'no response')def main():    sites = (        'http://penny-arcade.com/',        'http://reallifecomics.com/',        'http://sinfest.net/',        'http://userfriendly.org/',        'http://savagechickens.com/',        'http://xkcd.com/',        'http://duelinganalogs.com/',        'http://cad-comic.com/',        'http://samandfuzzy.com/',    )    workers = 4    work_queue = Queue()    done_queue = Queue()    processes = []    for url in sites:        work_queue.put(url)    for w in xrange(workers):        p = Process(target=worker, args=(work_queue, done_queue))        p.start()        processes.append(p)        work_queue.put('STOP')    for p in processes:        p.join()    done_queue.put('STOP')    for status in iter(done_queue.get, 'STOP'):        print statusif __name__ == '__main__':    main()