Python package - aiohttp has a warning message "Unclosed client session"

Question

My code is as follows:

import asyncio
import aiohttp

urls = [
    'http://www.163.com/',
    'http://www.sina.com.cn/',
    'https://www.hupu.com/',
    'http://www.csdn.net/'
]

async def get_url_data(u):
    """
    read url data
    :param u:
    :return:
    """
    print('running ', u)
    resp = await aiohttp.ClientSession().get(url=u)
    headers = resp.headers
    print(u, headers)
    return headers


async def request_url(u):
    """
    main func
    :param u:
    :return:
    """
    res = await get_url_data(u)
    return res

loop = asyncio.get_event_loop()
task_lists = asyncio.wait([request_url(u) for u in urls])
loop.run_until_complete(task_lists)
loop.close()

When i running my code, it's display a warning message: Unclosed client session

Anybody can give me some solutions about that?

Thanks a lot

Answer 1

You should close the connection in the end. You have 2 options:

You can close the connection manually:

import aiohttp
session = aiohttp.ClientSession()
# use the session here
session.close()

Or you can use it with a contex manager:

import aiohttp
import asyncio

async def fetch(client):
    async with client.get('http://python.org') as resp:
        assert resp.status == 200
        return await resp.text()

async def main(loop):
    async with aiohttp.ClientSession(loop=loop) as client:
        html = await fetch(client)
        print(html)

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

The client session supports the context manager protocol for self closing.