自学教程：总结python多进程multiprocessing的相关知识

import multiprocessing as mpfrom time import sleep# 进程执行函数def fun():    print("开始一个进程")    sleep(3)    print("进程结束")# 创建进程对象p = mp.Process(target = fun)p.start()   # 启动进程p.join()    # 回收进程

import multiprocessing as mpfrom time import sleep# 进程执行函数def fun():    print("开始一个进程")    sleep(3)    print("进程结束")# 创建进程对象p = mp.Process(target = fun)    # 把fun函数作为独立子进程 其它函数由进程来执行p.start()   # 启动进程sleep(2)print("父进程执行内容")p.join()    # 回收进程print("===============")"""pid = os.forkif pid == 0    fun()    os._exit(0)else:    os.wait()"""

import multiprocessing as mpfrom time import sleepa = 1# 进程执行函数def fun():    print("开始一个进程")    sleep(3)    global a    print("a=", a)    a = 1000    print("a=", a)    print("进程结束")# 创建进程对象p = mp.Process(target = fun)    # 把fun函数作为独立子进程 其它函数由进程来执行p.start()   # 启动进程sleep(2)print("父进程执行内容")p.join()    # 回收进程print("===============")print("a=", a)

"""创建多个进程"""from multiprocessing import Processimport osfrom time import sleepdef fun1():    sleep(2)    print(os.getppid(), '--', os.getpid(), "吃饭")def fun2():    sleep(3)    print(os.getppid(), '--', os.getpid(), "睡觉")def fun3():    sleep(4)    print(os.getppid(), '--', os.getpid(), "学习")jobs =[]for th in [fun1, fun2, fun3]:    p = Process(target = th)    jobs.append(p)    p.start()for i in jobs:    i.join()

from multiprocessing import Processfrom time import sleep# 含有参数的进程函数def worker(sec, name):    for i in range(3):        sleep(sec)        print("I'm %s"%name)        print("I'm working...")# p = Process(target = worker, args = (2, "Tom"))p = Process(target = worker, kwargs = {'name':'tom', 'sec': 2})p.start()p.join()

from multiprocessing import Processimport osfilename = './dace.jpg'size = os.path.getsize(filename)# 复制上半部分def up():    fr = open(filename, 'rb')    fw = open('bot,jpg', 'wb')    n = size//2    fw.write(fr.read(n))    fw.close()    fr.close()# 复制下半部分def down():    fr = open(filename, 'rb')    fw = open('bot,jpg', 'wb')    fr.seek(size//2.0)    fw.write(fr.read())    fw.close()    fr.close()p = Process(target = up)q = Process(target = down)p.start()q.start()p.join()q.join()