• 【python】多进程学习


    来源:廖雪峰

    讲解看来源吧 把例子记一下

    1.用fork创建进程

    import os
    
    print "Process (%s) start..." % os.getpid()
    pid = os.fork()
    if pid == 0:
        print 'I am child process (%s) and my parent is %s' % (os.getpid(), os.getppid())
    else:
        print 'I (%s) just created a child process (%s)' % (os.getpid(), pid)

    2.用Process创建进程

    import os
    from multiprocessing import Process
    
    def run_proc(name):
        print 'Run child process %s (%s)...' % (name, os.getpid())
    
    if __name__ == '__main__':
        print 'Parent process %s.' % os.getpid()
        p = Process(target = run_proc, args=('test',))
        print 'Process will start'
        p.start()
        p.join()
        print 'Process end'

    3.进程池Pool

    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)  #指定同时跑9个进程  如果用Pool(),则同时跑cpu核数个进程
        for i in range(9):
            p.apply_async(long_time_task, args=(i,))
        print 'Waiting for all subprocesses done...'
        p.close()
        p.join()
        print 'All subprocesses done'

    4.用Queue实现进程间通信

    from multiprocessing import Process, Queue
    import os, time, random
    
    def write(q):
        for value in "ABC":
            print 'Put %s to queue...' % value
            q.put(value)
            time.sleep(random.random())
    
    def read(q):
        while True:
            value = q.get(True)
            print 'Get %s from queue.' % value
            
    if __name__ == '__main__':
        q = Queue()
        pw = Process(target=write, args=(q,))
        pr = Process(target=read, args=(q,))
        pw.start()
        pr.start()
        pw.join()
        pr.terminate()
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  • 原文地址:https://www.cnblogs.com/dplearning/p/5822089.html
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