事件循环

事件循环＋回调（驱动生成器）＋ epoll（IO多路复用）

asyncio 是python用于解决异步IO编程的一整套解决方案

import asyncio
import time


async def get_html(url):
    print("get url start")
    await asyncio.sleep(2)
    print("get url end")
    return 'dylan'


if __name__ == "__main__":
    start_time = time.time()
    loop = asyncio.get_event_loop()        # 开始循环
    tasks = [get_html('http://www.baidu.com') for i in range(10)]
    loop.run_until_complete(asyncio.wait(tasks))        # asyncio.wait或者asyncio.gather是用于多任务，相当于多线程中的join方式，如果单个任务可以写成以下方式：
    # loop.run_until_complete(get_html('http://www.baidu.com'))
    print(time.time() - start_time)

# 从协程中获取返回值

if __name__ == "__main__":
    start_time = time.time()
    loop = asyncio.get_event_loop()
    get_return = asyncio.ensure_future(get_html('http://www.baidu.com'))
    loop.run_until_complete(get_return)
    print(get_return.result())

或者：

if __name__ == "__main__":
    start_time = time.time()
    loop = asyncio.get_event_loop()
    # get_return = asyncio.ensure_future(get_html('http://www.baidu.com'))
    task = loop.create_task(get_html('http://www.baidu.com'))
    loop.run_until_complete(task)
    print(task.result())

添加协程运作完后运作

from functools import partial

def callback(message, future):
    print('send email to someone {}'.format(message))

if __name__ == "__main__":
    start_time = time.time()
    loop = asyncio.get_event_loop()
    # get_return = asyncio.ensure_future(get_html('http://www.baidu.com'))
    task = loop.create_task(get_html('http://www.baidu.com'))
    task.add_done_callback(partial(callback, 'dylan'))
    # get_return.add_done_callback(partial(callback, 'dylan'))
    loop.run_until_complete(task)
    print(task.result())

# asyncio.wait和asyncio.gather的区别

gather比wait更高级

而调用方式：

        wait:            

if __name__ == "__main__":
    start_time = time.time()
    loop = asyncio.get_event_loop()
    tasks = [get_html('http://www.baidu.com') for i in range(10)]
    loop.run_until_complete(asyncio.wait(tasks))
    print(time.time() - start_time)

        gather:

if __name__ == "__main__":
    start_time = time.time()
    loop = asyncio.get_event_loop()
    tasks = [get_html('http://www.baidu.com') for i in range(10)]
    loop.run_until_complete(asyncio.gather(*tasks))
    print(time.time() - start_time)

       # 多组任务    

if __name__ == "__main__":
    start_time = time.time()
    loop = asyncio.get_event_loop()
    # tasks = [get_html('http://www.baidu.com') for i in range(10)]
    group1 = [get_html('http://www.baidu.com') for i in range(2)]
    group2 = [get_html('http://www.qq.com') for i in range(10)]
    # group1 = asyncio.gather(*group1)
    # group2 = asyncio.gather(*group2)
    loop.run_until_complete(asyncio.gather(*group1, *group2))
    print(time.time() - start_time)

if __name__ == "__main__":
    start_time = time.time()
    loop = asyncio.get_event_loop()
    # tasks = [get_html('http://www.baidu.com') for i in range(10)]
    group1 = [get_html('http://www.baidu.com') for i in range(2)]
    group2 = [get_html('http://www.qq.com') for i in range(10)]
    group1 = asyncio.gather(*group1)
    group2 = asyncio.gather(*group2)
    loop.run_until_complete(asyncio.gather(group1, group2))
    print(time.time() - start_time)