python 进程

linux 多进程

Unix/Linux操作系统提供了一个fork()系统调用

特点：

• fork()调用一次，返回两次
  - 当前进程复制了一份（父进程），生成子进程
  -
• 子进程返回0
• 父进程返回子进程的ID

fork 只存在linux，windows无法运行
linux 运行：

import os

print('Process (%s) start...' % os.getpid())
# Only works on Unix/Linux/Mac:
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))

运行结果：

Process (876) start...
I (876) just created a child process (877).
I am child process (877) and my parent is 876.

跨平台多进程

multiprocessing

multiprocessing模块是跨平台版本的多进程模块

例子：

from multiprocessing import Process
import os

# 子进程要执行的代码
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('Child process will start.')
    p.start()
    p.join()
    print('Child process end.')

pool

变量共享,使用manager

from multiprocessing import Pool, Manager


def func(my_list, my_dict):
    my_list.append(10)
    my_list.append(11)
    my_dict['a'] = 1
    my_dict['b'] = 2


if __name__ == '__main__':
    manager = Manager()
    my_list = manager.list()
    my_dict = manager.dict()

    pool = Pool(processes=2)
    for i in range(0, 2):
        pool.apply_async(func, (my_list, my_dict))
    pool.close()
    pool.join()

    print(my_list)
    print(my_dict)