存在的问题：ValueError: too many file descriptors in select()
原因分析：asyncio内部用到了select，而select就是系统打开文件数是有限度的，操作系统的限制，linux打开文件的最大数默认是1024，windows默认是509，超过了这个值，程序就开始报错
解决方法1：限制并发量

1. 首先，定义一个run协程函数

async def run():
    semaphore = asyncio.Semaphore(500) # 限制并发量为500
    to_get = [get_data(url.format(), semaphore) for url in urls] 
    await asyncio.wait(to_get)

其中get_data(url,semaphore)也是一个协程函数，即限制这个协程函数的并发数量，url为待请求的链接地址

2. 在限制并发量的协程函数中添加如下语句：

async with semaphore:

如下图所示，由

async def get_data(url, semaphore):    
    async with aiohttp.ClientSession() as session:
        async with session.get(url=myUrl, headers=headers) as response:

 变成

async def get_data(url, semaphore): 
    async with semaphore:   
        async with aiohttp.ClientSession() as session:
            async with session.get(url=myUrl, headers=headers) as response:

3.  在实现协程函数的实例中，添加如下语句即可

loop = asyncio.get_event_loop()
loop.run_until_complete(run())

实例参考

#coding:utf-8
import 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__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(run())
    loop.close()