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Async http client/server framework (asyncio)

Project description

Async http client/server framework

aiohttp logo

aiohttp 2.0 release!

For this release we completely refactored low-level implementation of http handling. Finally uvloop gives performance improvement. Overall performance improvement should be around 70-90% compared to 1.x version.

We took opportunity to refactor long standing api design problems across whole package. Client exceptions handling has been cleaned up and now much more straight forward. Client payload management simplified and allows to extend with any custom type. Client connection pool implementation has been redesigned as well, now there is no need for actively releasing response objects, aiohttp handles connection release automatically.

Another major change, we moved aiohttp development to public organization

With this amount of api changes we had to make backward incompatible changes. Please check this migration document

Please report problems or annoyance with with api to


  • Supports both client and server side of HTTP protocol.
  • Supports both client and server Web-Sockets out-of-the-box.
  • Web-server has middlewares and pluggable routing.

Getting started


To retrieve something from the web:

import aiohttp
import asyncio

async def fetch(session, url):
    with aiohttp.Timeout(10, loop=session.loop):
        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, '')

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


This is simple usage example:

from aiohttp import web

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

async def wshandler(request):
    ws = web.WebSocketResponse()
    await ws.prepare(request)

    async for msg in ws:
        if msg.type == web.MsgType.text:
            await ws.send_str("Hello, {}".format(
        elif msg.type == web.MsgType.binary:
            await ws.send_bytes(
        elif msg.type == web.MsgType.close:

    return ws

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


Note: examples are written for Python 3.5+ and utilize PEP-492 aka async/await. If you are using Python 3.4 please replace await with yield from and async def with @coroutine e.g.:

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

should be replaced by:

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

Discussion list

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


Optionally you may install the cChardet and aiodns libraries (highly recommended for sake of speed).


aiohttp is offered under the Apache 2 license.


The aiohttp community would like to thank Keepsafe ( for it’s support in the early days of the project.

Source code

The latest developer version is available in a github repository:


If you are interested in by efficiency, AsyncIO community maintains a list of benchmarks on the official wiki:


2.0.7 (2017-04-12)

  • Fix pypi distribution
  • Fix exception description #1807
  • Handle socket error in FileResponse #1773
  • Cancel websocket heartbeat on close #1793

2.0.6 (2017-04-06)

  • Fix web.run_app not to bind to default host-port pair if only socket is passed #1786
  • Keeping blank values for and multipart.form() #1765
  • TypeError in ResponseHandler.data_received #1770

2.0.5 (2017-03-29)

  • Memory leak with aiohttp.request #1756
  • Disable cleanup closed ssl transports by default.
  • Exception in request handling if the server responds before the body is sent #1761

2.0.4 (2017-03-27)

  • Memory leak with aiohttp.request #1756
  • Encoding is always UTF-8 in POST data #1750
  • Do not add “Content-Disposition” header by default #1755

2.0.3 (2017-03-24)

  • Call https website through proxy will cause error #1745
  • Fix exception on multipart/form-data post if content-type is not set #1743

2.0.2 (2017-03-21)

  • Fixed Application.on_loop_available signal #1739
  • Remove debug code

2.0.1 (2017-03-21)

  • Fix allow-head to include name on route #1737
  • Fixed AttributeError in WebSocketResponse.can_prepare #1736

2.0.0 (2017-03-20)

  • Added json to ClientSession.request() method #1726
  • Added session’s raise_for_status parameter, automatically calls raise_for_status() on any request. #1724
  • response.json() raises ClientReponseError exception if response’s content type does not match #1723
  • Cleanup timer and loop handle on any client exception.
  • Deprecate loop parameter for Application’s constructor

2.0.0rc1 (2017-03-15)

  • Properly handle payload errors #1710
  • Added ClientWebSocketResponse.get_extra_info() #1717
  • It is not possible to combine Transfer-Encoding and chunked parameter, same for compress and Content-Encoding #1655
  • Connector’s limit parameter indicates total concurrent connections. New limit_per_host added, indicates total connections per endpoint. #1601
  • Use url’s raw_host for name resolution #1685
  • Change ClientResponse.url to yarl.URL instance #1654
  • Add max_size parameter to web.Request reading methods #1133
  • Web stores data in temp files #1469
  • Add the allow_head=True keyword argument for add_get #1618
  • run_app and the Command Line Interface now support serving over Unix domain sockets for faster inter-process communication.
  • run_app now supports passing a preexisting socket object. This can be useful e.g. for socket-based activated applications, when binding of a socket is done by the parent process.
  • Implementation for Trailer headers parser is broken #1619
  • Fix FileResponse to not fall on bad request (range out of file size)
  • Fix FileResponse to correct stream video to Chromes
  • Deprecate public low-level api #1657
  • Deprecate encoding parameter for ClientSession.request() method
  • Dropped aiohttp.wsgi #1108
  • Dropped version from ClientSession.request() method
  • Dropped websocket version 76 support #1160
  • Dropped: aiohttp.protocol.HttpPrefixParser #1590
  • Dropped: Servers response’s .started, .start() and .can_start() method #1591
  • Dropped: Adding sub app via app.router.add_subapp() is deprecated use app.add_subapp() instead #1592
  • Dropped: Application.finish() and Application.register_on_finish() #1602
  • Dropped: web.Request.GET and web.Request.POST
  • Dropped: aiohttp.get(), aiohttp.options(), aiohttp.head(),, aiohttp.put(), aiohttp.patch(), aiohttp.delete(), and aiohttp.ws_connect() #1593
  • Dropped: aiohttp.web.WebSocketResponse.receive_msg() #1605
  • Dropped: ServerHttpProtocol.keep_alive_timeout attribute and keep-alive, keep_alive_on, timeout, log constructor parameters #1606
  • Dropped: TCPConnector’s` .resolve, .resolved_hosts, .clear_resolved_hosts() attributes and resolve constructor parameter #1607
  • Dropped ProxyConnector #1609

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