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)