【python】多进程学习

时间：2022-12-06 07:56:49

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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