async/await

python3.5又加入了async/await特性.
异步处理比同步处理能提升成百上千倍的效率，弥补了python由于GIL（全局锁）的存在，不能发挥多核的优势性能方面的短板.

普通 io

import time
import asyncio

def __my_fun(future, para:int):
    print('para is: {}'.format(para))
    result = para+1
   future.set_result(result)

async def my_fun(para):
    loop = asyncio.get_event_loop()
    future = loop.create_future()
    loop.call_soon(__my_fun, future, para)
    result = await future
    return result

async def hello(para, result:list):
    one_result = await my_fun(para)
   result.append(one_result)
    print('Hello World:%s' % time.time())

if __name__ =='__main__':
    loop = asyncio.get_event_loop()
    result = []
    tasks = [hello(i, result) for i in range(5)]
   loop.run_until_complete(asyncio.wait(tasks))
    print(result)

aiohttp

import time
import asyncio
from aiohttp import ClientSession

tasks = []
url = "https://www.baidu.com/{}"

# url paramater
async def hello(url):
    async with ClientSession() as session:
       async with session.get(url) as response:
          print('Hello World:%s' % time.time())
           return await response.read()

def run():
    for i in range(5):
       # future can return result
       task = asyncio.ensure_future(hello(url.format(i)))
       tasks.append(task)

    # get result
    result = loop.run_until_complete(asyncio.gather(*tasks))
    print(result)

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    run()

限制并发量

#coding:utf-8
import time,asyncio,aiohttp


url = 'https://www.baidu.com/'
async def hello(url,semaphore):
    async with semaphore:
       async with aiohttp.ClientSession() as session:
           async with session.get(url) as response:
              return await response.read()


async def run():
    semaphore = asyncio.Semaphore(500) # 限制并发量为500
    to_get = [hello(url.format(),semaphore) for _ in range(1000)] #总共1000任务
    await asyncio.wait(to_get)


if __name__ == '__main__':
#    now=lambda :time.time()
    loop = asyncio.get_event_loop()
   loop.run_until_complete(run())
    loop.close()