【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()