python中的多进程运用

本文链接：https://blog.csdn.net/weixin_40313634/article/details/100937313

1. 程序中另起进程

代码语言：javascript复制

from multiprocessing import Process
from os import getpid
from time import sleep

def run_time(name):
    sleep(5)
    print('child progress {}: {}'.format(name, getpid()))

if __name__ == '__main__':
    print('parent progress id: {}'.format(getppid()))  # os.getpid(): 获取当前进程ID; os.getppid(): 获取父进程ID
    p = Process(target=run_time, args=('hello_world',))  # 初始化子进程：target=目前函数名， args=参数
    print('start child progress')
    p.start()  # 启动子进程
    p.join()  # 进程同步：等待子进程执行完毕，程序再向下执行
    print('end child progress')

方法

getppid()、getpid()
p.start()
p.join()
Process(target=, args=(,))
Pool(n)
p.apply_async(, args=(,))
subprocess.call([’’, ‘’])
Queue()
q.put(value)
q.get(True)

2. 进程池

代码语言：javascript复制

from multiprocessing import Pool
from os import getpid
from time import sleep

def long_time_task(name):
    sleep(5)
    print('child process {0}: {1}n'.format(name, getpid()))

if __name__ == '__main__':
    print('parent process: {0}n'.format(getpid()))
    p = Pool(2)  ## 初始化进程池：一次可并行执行2个进程（等这两个执行结束，再次启动执行接下来的两个，和电脑是几核的无关）

    for i in range(10):
        p.apply_async(long_time_task, args=(i,))  ## 进程池添加进程
    print('start child progressn')
    p.close()  ## 关闭进程池（不能再添加新进程了），准备执行进程
    p.join()  # 进程同步
    print('end child progressn')

3. 问题：无法获取子进程的执行结果 -> 子进程

代码语言：javascript复制

import subprocess

print('nslookup www.python.org')
r = subprocess.call(['nslookup', 'www.python.org'])
print('Exit code: {}'.format(r))

4. 进程间通信

队列：Queue

代码语言：javascript复制

from multiprocessing import Process, Queue
from time import sleep
from random import random

def write(q):
    for i in range(5):
        print('puts {}'.format(i))
        q.put(i)
        sleep(1)

def read(q):
    sleep(10)
    while True:
        i = q.get(True)
        print('get {}'.format(i))

if __name__ == '__main__':
    q = Queue()
    pw = Process(target=write, args=(q,))
    pr = Process(target=read, args=(q,))
    print('START')
    pw.start()
    pr.start()
    pw.join()
    while True:
        if q.empty():  # 如果队列中的数据都处理完了，则强制停止read方法
            pr.terminate()
            break
    print('END')

信号量：Semaphore

代码语言：javascript复制

from multiprocessing import Process, Semaphore
from time import sleep

def write(f):
    f.acquire()
    sleep(5)
    f.release()
    
    
if __name__ == '__main__':
    pp = []
    f = Semaphore(1)
    for i in range(5):
        p = Process(target=write, args=(f,))
        p.start()
        pp.append(p)
    for p in pp:
        p.join()

join pool queue semaphore target

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