aiohttp.ClientSession

Learn async HTTP with aiohttp.ClientSession.

aiohttp.ClientSession

aiohttp.ClientSession is the session class for asynchronous HTTP requests. By making many requests on the same session, you reuse connections.

import asyncio
import aiohttp

async def main():
    async with aiohttp.ClientSession() as session:
        async with session.get("https://example.com") as resp:
            print(await resp.text())

The session is opened with an async with block and closes automatically when done. Requests are made with methods like session.get and session.post.

The async with block

async with is the asynchronous context manager. It ensures the session and response open and close safely. On block exit, __aexit__ is called automatically.

async with aiohttp.ClientSession() as session:
    async with session.get(url) as resp:
        body = await resp.text()

Two nested async with blocks are used: outer for the session, inner for the response. This way the connection is released after the body is read.

Exercise Async request with ClientSession

Start with import asyncio and import aiohttp. Inside async def main() open async with aiohttp.ClientSession() as session:. Inside it make the request with async with session.get("https://example.com") as resp: and print the body with print(await resp.text()). Finally add asyncio.run(main()).

Show example solution

import asyncio
import aiohttp

# Define a fake session for testing
class _S:
    async def __aenter__(self): return self
    async def __aexit__(self, *a): return False
    def get(self, url): return self
    async def text(self): return 'merhaba'

aiohttp.ClientSession = _S

async def main():
    async with aiohttp.ClientSession() as session:
        async with session.get('https://example.com') as resp:
            print(await resp.text())

asyncio.run(main())

Test yourself

Complete the ClientSession call

import aiohttp

async with ____() as session:

Show answer

import aiohttp

async with aiohttp.ClientSession() as session:

What does async with aiohttp.ClientSession() provide?
- Caching of the response
- Automatic closing of the session
- Making the request twice
- Changing the port number
Show answer

Automatic closing of the session — async with closes the session automatically on block exit.
Match the ClientSession concepts

ClientSession

Opens a session
async with

Closes automatically
session.get

Makes a GET request
await resp.text

Returns body

Next lesson: async get

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