asyncio 是在 Python 3.4 中引入的异步 IO 标准库.
简单介绍一下什么是同步 IO / 异步 IO.
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同步 IO: 你和女朋友去约会, 你需要一直等着她来, 之后你才能和她吃饭.
异步 IO: 你和女朋友去约会, 在她来的路上你不用一直等着, 可以去买礼物什么的.
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async/await/future
Python 3.5 引出的语法糖
async 创建协程, await 当协程阻塞时将其挂起并让步操作给其它协程, future 包装协程.
通过 asyncio.sleep() 模拟 IO 操作.
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import asyncio
async def hello(s):
print('Waiting '+str(s))
await asyncio.sleep(s)
print('Done '+str(s))
return 'Res '+str(s)
tasks = [
asyncio.ensure_future(hello(1)),
asyncio.ensure_future(hello(2)),
asyncio.ensure_future(hello(3))
]
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait(tasks))
for task in tasks:
print(task.result())
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输出
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Waiting 1
Waiting 2
Waiting 3
Done 1
Done 2
Done 3
Res 1
Res 2
Res 3
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callback
当协程执行完毕时调用 callback
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import asyncio
async def hello():
print('Hello World')
def callback(future):
print('Done')
coro = asyncio.ensure_future(hello())
coro.add_done_callback(callback)
loop = asyncio.get_event_loop()
loop.run_until_complete(coro)
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输出
aiohttp
aiohttp 是基于 asyncio 的 HTTP 框架.
aiohttp.request 用于发起 HTTP 请求.
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import asyncio
import aiohttp
async def req(s):
print('Requesting '+str(s))
async with aiohttp.request('GET',s) as response:
res = await response.read()
print('Receiving from '+str(s))
urls = ['http://www.baidu.com/','http://www.qq.com','http://www.163.com/']
tasks = []
for url in urls:
coro = asyncio.ensure_future(req(url))
tasks.append(coro)
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait(tasks))
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输出
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Requesting http://www.baidu.com/
Requesting http://www.qq.com
Requesting http://www.163.com/
Receiving from http://www.baidu.com/
Receiving from http://www.qq.com
Receiving from http://www.163.com/
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aiohttp.ClientSession 同样也能发起 HTTP 请求.
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import asyncio
import aiohttp
async def req(s):
print('Requesting '+str(s))
async with aiohttp.ClientSession() as session:
async with session.get(s) as response:
res = await response.read()
print('Receiving from '+str(s))
urls = ['http://www.baidu.com/','http://www.qq.com','http://www.163.com/']
tasks = []
for url in urls:
coro = asyncio.ensure_future(req(url))
tasks.append(coro)
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait(tasks))
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输出
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Requesting http://www.baidu.com/
Requesting http://www.qq.com
Requesting http://www.163.com/
Receiving from http://www.baidu.com/
Receiving from http://www.qq.com
Receiving from http://www.163.com/
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