Python协程之gevent_python gevent获取值

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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
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2. gevent的使用

import gevent

def work(n):
    for i in range(n):
        # 获取当前协程
        print(gevent.getcurrent(), i)

g1 = gevent.spawn(work, 5)
g2 = gevent.spawn(work, 5)
g3 = gevent.spawn(work, 5)
g1.join()
g2.join()
g3.join()
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运行结果

<Greenlet at 0x10e49f550: f(5)> 0
<Greenlet at 0x10e49f550: f(5)> 1
<Greenlet at 0x10e49f550: f(5)> 2
<Greenlet at 0x10e49f550: f(5)> 3
<Greenlet at 0x10e49f550: f(5)> 4
<Greenlet at 0x10e49f910: f(5)> 0
<Greenlet at 0x10e49f910: f(5)> 1
<Greenlet at 0x10e49f910: f(5)> 2
<Greenlet at 0x10e49f910: f(5)> 3
<Greenlet at 0x10e49f910: f(5)> 4
<Greenlet at 0x10e49f4b0: f(5)> 0
<Greenlet at 0x10e49f4b0: f(5)> 1
<Greenlet at 0x10e49f4b0: f(5)> 2
<Greenlet at 0x10e49f4b0: f(5)> 3
<Greenlet at 0x10e49f4b0: f(5)> 4
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可以看到，3个greenlet是依次运行而不是交替运行

3. gevent切换执行

import gevent

def work(n):
    for i in range(n):
        # 获取当前协程
        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(work, 5)
g2 = gevent.spawn(work, 5)
g3 = gevent.spawn(work, 5)
g1.join()
g2.join()
g3.join()

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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

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4. 给程序打补丁

import gevent
import time
from gevent import monkey

# 打补丁，让gevent框架识别耗时操作，比如：time.sleep，网络请求延时
monkey.patch_all()


# 任务1
def work1(num):
    for i in range(num):
        print("work1....")
        time.sleep(0.2)
        # gevent.sleep(0.2)

# 任务1
def work2(num):
    for i in range(num):
        print("work2....")
        time.sleep(0.2)
        # gevent.sleep(0.2)



if __name__ == '__main__':
    # 创建协程指定对应的任务
    g1 = gevent.spawn(work1, 3)
    g2 = gevent.spawn(work2, 3)

    # 主线程等待协程执行完成以后程序再退出
    g1.join()
    g2.join()
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运行结果

work1....
work2....
work1....
work2....
work1....
work2....
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5. 注意

• 当前程序是一个死循环并且还能有耗时操作，就不需要加上join方法了,因为程序需要一直运行不会退出

示例代码

import gevent
import time
from gevent import monkey

# 打补丁，让gevent框架识别耗时操作，比如：time.sleep，网络请求延时
monkey.patch_all()


# 任务1
def work1(num):
    for i in range(num):
        print("work1....")
        time.sleep(0.2)
        # gevent.sleep(0.2)

# 任务1
def work2(num):
    for i in range(num):
        print("work2....")
        time.sleep(0.2)
        # gevent.sleep(0.2)



if __name__ == '__main__':
    # 创建协程指定对应的任务
    g1 = gevent.spawn(work1, 3)
    g2 = gevent.spawn(work2, 3)

    while True:
        print("主线程中执行")
        time.sleep(0.5)
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执行结果:

主线程中执行
work1....
work2....
work1....
work2....
work1....
work2....
主线程中执行
主线程中执行
主线程中执行
..省略..
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