多进程

Table of Contents

  1. 写多进程的方法
    1. 进程池
    2. 非进程池

写多进程的方法

进程池

如果要启动大量的子进程，可以用进程池的方式批量创建子进程：

#!/bin/env python
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(4)
    for i in range(5):
        p.apply_async(long_time_task, args=(i,))
    print('Waiting for all subprocesses done...')
    p.close()
    p.join()
    print('All subprocesses done.')

对Pool对象调用join()方法会等待所有子进程执行完毕，调用join()之前必须先调用close()，调用close()之后就不能继续添加新的Process了。

非进程池

#!/bin/env python
from multiprocessing import Process
import os
import time

def run_proc(name):
    time.sleep(3)
    print 'Run child process %s (%s)...' % (name, os.getpid())

if __name__=='__main__':
    print 'Parent process %s.' % os.getpid()
    processes = list()
    for i in range(5):
        p = Process(target=run_proc, args=('test',))
        print 'Process will start.'
        p.start()
        processes.append(p)

    for p in processes:
        p.join()
    print 'Process end.'