HTTP client/server for asyncio (PEP 3156).


Library Installation

$ pip install aiohttp

You may want to install optional cchardet library as faster replacement for chardet:

$ pip install cchardet

For speeding up DNS resolving by client API you may install aiodns as well. This option is highly recommended:

$ pip install aiodns

Getting Started

Client example:

import aiohttp
import asyncio
import async_timeout

async def fetch(session, url):
    with async_timeout.timeout(10):
        async with session.get(url) as response:
            return await response.text()

async def main(loop):
    async with aiohttp.ClientSession(loop=loop) as session:
        html = await fetch(session, '')

loop = asyncio.get_event_loop()

Server example:

from aiohttp import web

async def handle(request):
    name = request.match_info.get('name', "Anonymous")
    text = "Hello, " + name
    return web.Response(text=text)

app = web.Application()
app.router.add_get('/', handle)
app.router.add_get('/{name}', handle)



Throughout this documentation, examples utilize the async/await syntax introduced by PEP 492 that is only valid for Python 3.5+.

If you are using Python 3.4, please replace await with yield from and async def with a @coroutine decorator. For example, this:

async def coro(...):
    ret = await f()

should be replaced by:

def coro(...):
    ret = yield from f()


Polls tutorial

Source code

The project is hosted on GitHub

Please feel free to file an issue on the bug tracker if you have found a bug or have some suggestion in order to improve the library.

The library uses Travis for Continuous Integration.


  • Python 3.4.2+

  • chardet library

  • multidict library

  • async_timeout library

  • Optional cchardet library as faster replacement for chardet.

    Install it explicitly via:

    $ pip install cchardet
  • Optional aiodns library for fast DNS resolving. The library is highly recommended.

    $ pip install aiodns

Discussion list

aio-libs google group:!forum/aio-libs

Feel free to post your questions and ideas here.


Please read the instructions for contributors before making a Pull Request.

Authors and License

The aiohttp package is written mostly by Nikolay Kim and Andrew Svetlov.

It’s Apache 2 licensed and freely available.

Feel free to improve this package and send a pull request to GitHub.

Policy for Backward Incompatible Changes

aiohttp keeps backward compatibility.

After deprecating some Public API (method, class, function argument, etc.) the library guaranties the usage of deprecated API is still allowed at least for a year and half after publishing new release with deprecation.

All deprecations are reflected in documentation and raises DeprectaionWarning.

Sometimes we are forced to break the own rule for sake of very strong reason. Most likely the reason is a critical bug which cannot be solved without major API change, but we are working hard for keeping these changes as rare as possible.


Indices and tables

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