python 协程

协程

协程就是一种用户态内的上下文切换技术.

1.使用gevent实现协程, gevent.spawn()调用函数,  gevent.sleep(1) 模拟阻塞,实现切换.

import gevent
import time


def foo():
    print('running in foo',time.ctime())
    gevent.sleep(1)
    print('Explicit context switch to foo again',time.ctime())


def bar():
    print('running in foo', time.ctime())
    gevent.sleep(2)
    print('EIxplicit context switch to foo again', time.ctime())

gevent.joinall([
    gevent.spawn(foo),
    gevent.spawn(bar)
])

 2.协程可以实现高并发,且占用的资源比进程和线程少.

#!/usr/bin/env python3
#  -*- coding=utf-8 -*-
from gevent import monkey
import gevent
monkey.patch_all()  #刷新
from urllib.request import urlopen
import time

def f(url):
    print('get:%s'%url)
    resp=urlopen(url)
    data=resp.read()
    print('%d bytes received from %s .' %(len(data),url))

l=['http://www.xiaohuar.com/hua/','http://www.zhihu.com/question/21653286','http://news.dahe.cn/2016/10-12/107590869.html']
start=time.time()

#协程方式
gevent.joinall([
    gevent.spawn(f,'http://www.xiaohuar.com/hua/'),
    gevent.spawn(f,'http://www.zhihu.com/question/21653286'),
    gevent.spawn(f,'http://news.dahe.cn/2016/10-12/107590869.html')
])

#普通方式
# for url in l:
#     f(url)

print(time.time()-start)