江苏龙网

  1. 主页 > 生活百科 > >

一文讲透 Python 协程( 三 )

Python 协程


 
4、协程4.1 协程的概念

协程，又称微线程，纤程,也称为用户级线程，在不开辟线程的基础上完成多任务，也就是在单线程的情况下完成多任务，多个任务按照一定顺序交替执行 通俗理解只要在def里面只看到一个yield关键字表示就是协程
协程是也是实现多任务的一种方式
 
协程yield的代码实现简单实现协程import timedef work1:while True:print("----work1---")yieldtime.sleep(0.5)def work2:while True:print("----work2---")yieldtime.sleep(0.5)def main:w1 = work1w2 = work2while True:next(w1)next(w2)if __name__ == "__main__":main运行结果：
----work1-------work2-------work1-------work2-------work1-------work2-------work1-------work2-------work1-------work2-------work1-------work2---...省略... 
小结协程之间执行任务按照一定顺序交替执行
 
5、greenlet5.1 greentlet的介绍为了更好使用协程来完成多任务，Python中的greenlet模块对其封装，从而使得切换任务变的更加简单
使用如下命令安装greenlet模块:
pip3 install greenlet使用协程完成多任务
import timeimport greenlet# 任务1def work1:for i in range(5):print("work1...")time.sleep(0.2)# 切换到协程2里面执行对应的任务g2.switch# 任务2def work2:for i in range(5):print("work2...")time.sleep(0.2)# 切换到第一个协程执行对应的任务g1.switchif __name__ == '__main__':# 创建协程指定对应的任务g1 = greenlet.greenlet(work1)g2 = greenlet.greenlet(work2)# 切换到第一个协程执行对应的任务g1.switch运行效果
work1...work2...work1...work2...work1...work2...work1...work2...work1...work2... 
6、gevent6.1 gevent的介绍greenlet已经实现了协程，但是这个还要人工切换，这里介绍一个比greenlet更强大而且能够自动切换任务的第三方库，那就是gevent 。
gevent内部封装的greenlet，其原理是当一个greenlet遇到IO(指的是input output 输入输出，比如网络、文件操作等)操作时，比如访问网络，就自动切换到其他的greenlet，等到IO操作完成，再在适当的时候切换回来继续执行 。
由于IO操作非常耗时，经常使程序处于等待状态，有了gevent为我们自动切换协程，就保证总有greenlet在运行，而不是等待IO
 
安装pip3 install gevent 
6.2 gevent的使用import geventdef work(n):for i in range(n):print(gevent.getcurrent, i)g1 = gevent.spawn(work, 5)g2 = gevent.spawn(work, 5)g3 = gevent.spawn(work, 5)g1.joing2.joing3.join运行结果
<Greenlet "Greenlet-0" at 0x26d8c970488: work(5)> 0<Greenlet "Greenlet-1" at 0x26d8c970598: work(5)> 0<Greenlet "Greenlet-2" at 0x26d8c9706a8: work(5)> 0<Greenlet "Greenlet-0" at 0x26d8c970488: work(5)> 1<Greenlet "Greenlet-1" at 0x26d8c970598: work(5)> 1<Greenlet "Greenlet-2" at 0x26d8c9706a8: work(5)> 1<Greenlet "Greenlet-0" at 0x26d8c970488: work(5)> 2<Greenlet "Greenlet-1" at 0x26d8c970598: work(5)> 2<Greenlet "Greenlet-2" at 0x26d8c9706a8: work(5)> 2<Greenlet "Greenlet-0" at 0x26d8c970488: work(5)> 3<Greenlet "Greenlet-1" at 0x26d8c970598: work(5)> 3<Greenlet "Greenlet-2" at 0x26d8c9706a8: work(5)> 3<Greenlet "Greenlet-0" at 0x26d8c970488: work(5)> 4<Greenlet "Greenlet-1" at 0x26d8c970598: work(5)> 4<Greenlet "Greenlet-2" at 0x26d8c9706a8: work(5)> 4可以看到，3个greenlet是依次运行而不是交替运行
 
6.3 gevent切换执行import geventdef work(n):for i in range(n):print(gevent.getcurrent, i)gevent.sleep(1)g1 = gevent.spawn(work, 5)g2 = gevent.spawn(work, 5)g3 = gevent.spawn(work, 5)g1.joing2.joing3.join运行结果
<Greenlet at 0x7fa70ffa1c30: f(5)> 0<Greenlet at 0x7fa70ffa1870: f(5)> 0<Greenlet at 0x7fa70ffa1eb0: f(5)> 0<Greenlet at 0x7fa70ffa1c30: f(5)> 1<Greenlet at 0x7fa70ffa1870: f(5)> 1<Greenlet at 0x7fa70ffa1eb0: f(5)> 1<Greenlet at 0x7fa70ffa1c30: f(5)> 2<Greenlet at 0x7fa70ffa1870: f(5)> 2<Greenlet at 0x7fa70ffa1eb0: f(5)> 2<Greenlet at 0x7fa70ffa1c30: f(5)> 3<Greenlet at 0x7fa70ffa1870: f(5)> 3<Greenlet at 0x7fa70ffa1eb0: f(5)> 3<Greenlet at 0x7fa70ffa1c30: f(5)> 4<Greenlet at 0x7fa70ffa1870: f(5)> 4<Greenlet at 0x7fa70ffa1eb0: f(5)> 4 
6.4 给程序打补丁import geventimport timefrom gevent import monkeymonkey.patch_alldef work1(num):for i in range(num):print("work1....")time.sleep(0.2)def work2(num):for i in range(num):print("work2....")time.sleep(0.2)if __name__ == '__main__':g1 = gevent.spawn(work1, 3)g2 = gevent.spawn(work2, 3)g1.joing2.join


推荐阅读


上一篇：喝剩黑茶用处多,如何泡黑茶

下一篇：没有了