协程greenlet、gevent

greenlet
为了更好使用协程来完成多任务，python中greenlet模块对其封装，从而使得切换任务变得更加简单
安装方式

pip3 install greenlet

示例代码：

from greenlet import greenlet
import time

def test1():
while True:
print("-----真-----")
gr2.switch()
time.sleep(0.5)

def test2():
while True:
print("-----真-----")
gr1.switch()
time.sleep(0.5)

gr1 = greenlet(test1)
gr2 = greenlet(test2)

# 切换到gr1中运行
gr1.swith() 

gevent
greenlet已经实现了协程，但是这个工人切换，是不是觉得太麻烦了，不要着急，python还有一个比greenlet更强大的并且能够自动切换任务的模块`gevent`
其原理是当一个greentlet遇到IO（指的是input ouput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完成，再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 

1.gevent的使用

import gevent

def f(n):
for i in range(n):
　　print(gevent.getcurrent(), i)

g1 = gevent.spawn(f, 5)
g2 = gevent.spawn(f, 5)
g3 = gevent.spawn(f, 5)
g1.join()
g2.join()
g3.join()

运行结果 

F:python3.6python.exe D:/pythonProjects/pynetwork/coroutine/gevent_demo.py
<Greenlet "Greenlet-0" at 0x22ef10f5c48: f(5)> 0
<Greenlet "Greenlet-0" at 0x22ef10f5c48: f(5)> 1
<Greenlet "Greenlet-0" at 0x22ef10f5c48: f(5)> 2
<Greenlet "Greenlet-0" at 0x22ef10f5c48: f(5)> 3
<Greenlet "Greenlet-0" at 0x22ef10f5c48: f(5)> 4
<Greenlet "Greenlet-1" at 0x22ef12dc048: f(5)> 0
<Greenlet "Greenlet-1" at 0x22ef12dc048: f(5)> 1
<Greenlet "Greenlet-1" at 0x22ef12dc048: f(5)> 2
<Greenlet "Greenlet-1" at 0x22ef12dc048: f(5)> 3
<Greenlet "Greenlet-1" at 0x22ef12dc048: f(5)> 4
<Greenlet "Greenlet-2" at 0x22ef12dc148: f(5)> 0
<Greenlet "Greenlet-2" at 0x22ef12dc148: f(5)> 1
<Greenlet "Greenlet-2" at 0x22ef12dc148: f(5)> 2
<Greenlet "Greenlet-2" at 0x22ef12dc148: f(5)> 3
<Greenlet "Greenlet-2" at 0x22ef12dc148: f(5)> 4

Process finished with exit code 0

gevent切换执行

import gevent

def f(n):
for i in range(n):
　　print(gevent.getcurrent(), i)
　　# 用来模拟一个耗时操作，注意不是time模块中的sleep
　　gevent.sleep(1)

g1 = gevent.spawn(f, 5)
g2 = gevent.spawn(f, 5)
g3 = gevent.spawn(f, 5)
g1.join()
g2.join()
g3.join()

运行结果 

F:python3.6python.exe D:/pythonProjects/pynetwork/coroutine/gevent_demo.py
<Greenlet "Greenlet-0" at 0x2c45e304c48: f(5)> 0
<Greenlet "Greenlet-1" at 0x2c45e4cc048: f(5)> 0
<Greenlet "Greenlet-2" at 0x2c45e4cc148: f(5)> 0
<Greenlet "Greenlet-0" at 0x2c45e304c48: f(5)> 1
<Greenlet "Greenlet-1" at 0x2c45e4cc048: f(5)> 1
<Greenlet "Greenlet-2" at 0x2c45e4cc148: f(5)> 1
<Greenlet "Greenlet-0" at 0x2c45e304c48: f(5)> 2
<Greenlet "Greenlet-1" at 0x2c45e4cc048: f(5)> 2
<Greenlet "Greenlet-2" at 0x2c45e4cc148: f(5)> 2
<Greenlet "Greenlet-0" at 0x2c45e304c48: f(5)> 3
<Greenlet "Greenlet-1" at 0x2c45e4cc048: f(5)> 3
<Greenlet "Greenlet-2" at 0x2c45e4cc148: f(5)> 3
<Greenlet "Greenlet-0" at 0x2c45e304c48: f(5)> 4
<Greenlet "Greenlet-1" at 0x2c45e4cc048: f(5)> 4
<Greenlet "Greenlet-2" at 0x2c45e4cc148: f(5)> 4

Process finished with exit code 0

3. 给程序打补丁

from gevent import monkey
import gevent
import random
import time

# 有耗时操作时需要
monkey.patch_all() # 将程序中用到的耗时操作的代码，换为gevent中自己实现的模块

def coroutine_work(coroutine_name):
for i in range(10):
print(coroutine_name, i)
time.sleep(random.random())

gevent.joinall([
gevent.spawn(coroutine_work, "work1"),
gevent.spawn(coroutine_work, "work2")
])

运行结果

F:python3.6python.exe D:/pythonProjects/pynetwork/coroutine/gevent_test.py
work1 0
work2 0
work2 1
work1 1
work1 2
work1 3
work2 2
work1 4
work1 5
work2 3
work1 6
work1 7
work2 4
work2 5
work1 8
work1 9
work2 6
work2 7
work2 8
work2 9

Process finished with exit code 0