18.多进程

学习网站：https://www.cnblogs.com/yuanchenqi/articles/6248025.html

进程创建使用：

方式1： 创建对象使用

from multiprocessing import Process


if __name__ == "__main__":


    def showNum(num):
        print(num)


    p_list = []
    for i in range(10):
        p = Process(target=showNum, args=("abc",))
        p_list.append(p)
        p.start()

    for i in p_list:
        i.join()

方式2：使用继承的方式使用

---

进程间通信：

方式1：使用进程队列multiprocessing

import queue,time

import multiprocessing
def foo(q):
    time.sleep(1)
    print("son process",id(q))
    q.put(123)
    q.put("yuan")

if __name__ == '__main__':
    #q=queue.Queue()
    q=multiprocessing.Queue()
    p=multiprocessing.Process(target=foo,args=(q,))
    p.start()
    #p.join()
    print("main process",id(q))
    print(q.get())
    print(q.get())

方式2：管道

from multiprocessing import Process, Pipe
def f(conn):
    conn.send([12, {"name":"yuan"}, 'hello'])
    response=conn.recv()
    print("response",response)
    conn.close()
    print("q_ID2:",id(conn))

if __name__ == '__main__':

    parent_conn, child_conn = Pipe() #双向管道

    print("q_ID1:",id(child_conn))
    p = Process(target=f, args=(child_conn,))
    p.start()

    print(parent_conn.recv())   # prints "[42, None, 'hello']"
    parent_conn.send("儿子你好!")
    p.join()

方式3：Managers
Queue和Pipe这是实现了数据交互，并没有实现数据共享，即一个进程去更改另一个进程中的数据。

from multiprocessing import Process, Manager

def f(d, l,n):

    d[n] = '1'    #{0:"1"}
    d['2'] = 2    #{0:"1","2":2}

    l.append(n)    #[0,1,2,3,4,   0,1,2,3,4,5,6,7,8,9]


if __name__ == '__main__':

    with Manager() as manager:
        d = manager.dict()#{}
        l = manager.list(range(5))#[0,1,2,3,4]

        p_list = []

        for i in range(10):
            p = Process(target=f, args=(d,l,i))
            p.start()
            p_list.append(p)

        for res in p_list:
            res.join()

---

---

进程同步：

使用multiprocessing模块下的lock

from multiprocessing import Process, Lock
import time

def f(l, i):

        l.acquire()
        time.sleep(1)
        print('hello world %s' % i)
        l.release()

if __name__ == '__main__':
    lock = Lock()

    for num in range(10):
        Process(target=f, args=(lock, num)).start()

---

---

进程池：

from  multiprocessing import Process,Pool
import time,os

def Foo(i):

    time.sleep(1)
    print(i)
    print("son",os.getpid())

    return "HELLO %s"%i


def Bar(arg):
    print(arg)
    # print("hello")
    # print("Bar:",os.getpid())

if __name__ == '__main__':

    pool = Pool(5)
    print("main pid",os.getpid())
    for i in range(100):
        #pool.apply(func=Foo, args=(i,))  #同步接口
        #pool.apply_async(func=Foo, args=(i,))

        #回调函数：  就是某个动作或者函数执行成功后再去执行的函数

        pool.apply_async(func=Foo, args=(i,),callback=Bar)

    pool.close()
    pool.join()         # join与close调用顺序是固定的

    print('end')