4.24作业

from multiprocessing import Process
import time
import random

def task(n):
    time.sleep(random.randint(1,3))
    print('------->%s' %n)

if __name__ == '__main__':
    p1 = Process(target=task,args=(1,))
    p2 = Process(target=task,args=(2,))
    p3 = Process(target=task,args=(3,))

    p1.start()
    p2.start()
    p3.start()
    print('----------->4')


效果1：最先输出---------->4并发

　　 p1.start()
    p2.start()
    p3.start()
    print('----------->4')

效果2：最后输出---------->4并发

#     p1.start()
#     p2.start()
#     p3.start()
#     p1.join()
#     p2.join()
#     p3.join()
#
#     print('----------->4')

效果3：顺序输出-------串行

#
#     p1.start()
#     p1.join()
#     p2.start()
#     p2.join()
#     p3.start()
#     p3.join()
#
#     print('----------->4')



套接字实现并发
   有问题存在：  不能无线并发，pid数目是有限的，不能无限并发

from socket import *
from multiprocessing import Process

server=socket(AF_INET,SOCK_STREAM)
server.setsockopt(SOL_SOCKET,SO_REUSEADDR,1)
server.bind(('127.0.0.1',8080))
server.listen(5)

def talk(conn,client_addr):
    while True:
        try:
            msg=conn.recv(1024)
            if not msg:break
            conn.send(msg.upper())
        except Exception:
            break

if __name__ == '__main__': #windows下start进程一定要写到这下面
    while True:
        conn,client_addr=server.accept()
        p=Process(target=talk,args=(conn,client_addr))
        p.start()

from socket import *

client=socket(AF_INET,SOCK_STREAM)
client.connect(('127.0.0.1',8080))


while True:
    msg=input('>>: ').strip()
    if not msg:continue

    client.send(msg.encode('utf-8'))
    msg=client.recv(1024)
    print(msg.decode('utf-8'))