Python之路【第十七篇】:Python并发编程|协程

一、协程

协程，又叫微线程，纤程。英文名Coroutine。协程本质上就是一个线程

优点1：协程极高的执行效率。因为子程序切换不是线程切换，而是由程序自身控制，因此，没有线程切换的开销，和多线程比，线程数量越多，协程的性能优势就越来越明显。(简单来说没有切换的消耗)

优点2：不需要多线程的锁机制，因为只有一个线程，也不存在同时写变量冲突，在协程中控制共享资源不加锁，只需要判断状态就好，所以执行效率比多线程高很多。(没有锁的概念)

因为协程是一个线程执行，那怎么利用多核CPU呢？最简单的方法是多进程+协程，既充分利用多核，又充分发挥协程的高效率，可获得极高的性能。

二、yield的简单实现

#_*_ coding:utf-8 _*_
# Author:Simon
# Datetime:2019/9/2 21:07
# Software:PyCharm

import time
import queue

def consumer(name):
    print("--->ready to eat baozi...")
    while True:
        new_baozi = yield
        print("[%s] is eating baozi %s" % (name,new_baozi)) #time.sleep(1) def producer(): r = con.__next__() r = con2.__next__() n = 0 while 1: time.sleep(1) print("\033[32;1m[producer]\033[0m is making baozi %s and %s" %(n,n+1) ) con.send(n) con2.send(n+1) n +=2 if __name__ == '__main__': con = consumer("c1") con2 = consumer("c2") p = producer()

三、Greenlet模块

greenlet是一个用C实现的协程模块，相比与python自带的yield，它可以使你在任意函数之间随意切换，而不需把这个函数先声明为generator

#_*_ coding:utf-8 _*_
# Author:Simon
# Datetime:2019/9/2 21:29
# Software:PyCharm
from greenlet import greenlet

def test1():
    print(12)
    gr2.switch()
    print(34)
    gr2.switch()
def test2():
    print(56) gr1.switch() print(78) gr1 = greenlet(test1) gr2 = greenlet(test2) gr1.switch()

四、Gevent模块

本质就是封装了greenlet模块，它能检测I/O并且遇到I/O自动切换到另外一个任务执行；可以帮我们提升效率

#_*_ coding:utf-8 _*_
# Author:Simon
# Datetime:2019/9/2 21:39
# Software:PyCharm

import gevent

import requests,time

start=time.time()

def f(url):
    print('GET: %s' % url)
    resp =requests.get(url) data = resp.text print('%d bytes received from %s.' % (len(data), url)) gevent.joinall([ gevent.spawn(f, 'https://www.jd.org/'), gevent.spawn(f, 'https://www.xiaohua.com/'), gevent.spawn(f, 'https://www.baidu.com/'), gevent.spawn(f, 'https://www.taobao.com/'), ]) # f('https://www.jd.org/') # f('https://www.xiaohua.com/') # f('https://baidu.com/') # f('https://www.taobao.com/') # # print("cost time:",time.time()-start)

gevent异步提交任务

from gevent import monkey;monkey.patch_all()
import gevent
import time

def eat(name):
    print('%s eat 1' % name)
    time.sleep(3) print('%s eat 2' % name) def play(name): print('%s play 1' % name) time.sleep(4) print('%s play 2' % name) g1=gevent.spawn(eat,'simon') g2=gevent.spawn(play,'zhuzhu') # time.sleep(5) # g1.join() # g2.join()  gevent.joinall([g1,g2]) #相当于上边两行代码  打印： simon eat 1 zhuzhu play 1 simon eat 2 zhuzhu play 2

基于gevent模块实现并发的套接字通信

单线程、多任务的I/O操作。

#基于gevent实现
from gevent import monkey,spawn;monkey.patch_all()
from socket import *

def communicate(conn):
    while True:
        try:
            data=conn.recv(1024)
            if not data:break conn.send(data.upper()) except ConnectionResetError: break conn.close() def server(ip,port): server = socket(AF_INET, SOCK_STREAM) server.bind((ip,port)) server.listen(5) while True: conn, addr = server.accept() spawn(communicate,conn) #造一个协程对象，提交完这个对象它不会执行  server.close() if __name__ == '__main__': g=spawn(server,'127.0.0.1',8090) g.join()

##客户端

from socket import *
from threading import Thread,currentThread

def client():
    client=socket(AF_INET,SOCK_STREAM)
    client.connect(('127.0.0.1',8090))

    while True:
        client.send(('%s hello' %currentThread().getName()).encode('utf-8')) data=client.recv(1024) print(data.decode('utf-8')) client.close() if __name__ == '__main__': for i in range(500): t=Thread(target=client) t.start()