asyncio 异步协程

1.并发执行任务示例：

 1 import asyncio, time
 2 
 3 #异步协程
 4 async def hello():
 5     """
 6     这边程序运行时，线程不会等待这个sleep 1s,将直接终端继续执行往下执行，这边5个任务会并发执行
 7     :return:
 8     """
 9     print("hello world")
10     asyncio.sleep(1)
11     print("Hello again! time:{}".format(time.time()))
12 
13 def run():
14     for i in range(5):
15         loop.run_until_complete(hello())
16 
17 if __name__ == "__main__":
18     loop = asyncio.get_event_loop()
19     run()
20     loop.close()
View Code

 执行结果:

 2.并发爬取网页内容示例：

 

 1 #通过asyncio 协程实现并发获取网站数据
 2 #await语法相当于 yield from
 3 import asyncio
 4 
 5 async def wget(host):
 6     print("wget {}...".format(host))
 7     connect = asyncio.open_connection(host, 80)
 8     reader, writer = await connect
 9     header = 'GET / HTTP/1.0\r\nHost: %s\r\n\r\n' % host
10     writer.write(header.encode('utf-8'))
11     await writer.drain()
12     result = ""
13     while True:
14         line = await reader.readline()
15         if not line:
16             break
17         result +='%s header > %s\n' % (host, line.decode('utf-8').rstrip())
18     writer.close()
19     return result
20 
21 loop = asyncio.get_event_loop()
22 tasks = [asyncio.ensure_future(wget(host)) for host in ['ncm.itsmsit.cnsuning.com', 'emm.cloudytrace.com']]
23 loop.run_until_complete(asyncio.wait(tasks))
24 for index, task in enumerate(tasks):
25     #获取任务执行的结果也就是wget()函数return的值
26     print("结果{}：".format(index))
27     print(task.result())
28 loop.close()
View Code

执行结果：

  3.异步协程详细介绍：

https://www.cnblogs.com/zhaof/p/8490045.html

 

posted @ 2018-11-27 19:19  啊行啊  阅读(163)  评论(0)  编辑  收藏  举报