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http client/server for asyncio

Project description

http client/server for asyncio

aiohttp logo


  • 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:
            ws.send_str("Hello, {}".format(
        elif msg.type == web.MsgType.binary:
        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.

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:


1.1.6 (2016-11-28)

  • Fix BodyPartReader.read_chunk bug about returns zero bytes before EOF #1428

1.1.5 (2016-11-16)

  • Fix static file serving in fallback mode #1401

1.1.4 (2016-11-14)

  • Make TestServer.make_url compatible with yarl.URL #1389

  • Generate informative exception on redirects from server which doesn’t provide redirection headers #1396

1.1.3 (2016-11-10)

  • Support root resources for sub-applications #1379

1.1.2 (2016-11-08)

  • Allow starting variables with an underscore #1379

  • Properly process UNIX sockets by gunicorn worker #1375

  • Fix ordering for FrozenList

  • Don’t propagate pre and post signals to sub-application #1377

1.1.1 (2016-11-04)

  • Fix documentation generation #1120

1.1.0 (2016-11-03)

  • Drop deprecated WSClientDisconnectedError (BACKWARD INCOMPATIBLE)

  • Use yarl.URL in client API. The change is 99% backward compatible but ClientResponse.url is an yarl.URL instance now. #1217

  • Close idle keep-alive connections on shutdown #1222

  • Modify regex in AccessLogger to accept underscore and numbers #1225

  • Use yarl.URL in web server API. web.Request.rel_url and web.Request.url are added. URLs and templates are percent-encoded now. #1224

  • Accept yarl.URL by server redirections #1278

  • Return yarl.URL by .make_url() testing utility #1279

  • Properly format IPv6 addresses by aiohttp.web.run_app #1139

  • Use yarl.URL by server API #1288

    • Introduce resource.url_for(), deprecate resource.url().

    • Implement StaticResource.

    • Inherit SystemRoute from AbstractRoute

    • Drop old-style routes: Route, PlainRoute, DynamicRoute, StaticRoute, ResourceAdapter.

  • Revert resp.url back to str, introduce resp.url_obj #1292

  • Raise ValueError if BasicAuth login has a “:” character #1307

  • Fix bug when ClientRequest send payload file with opened as open(‘filename’, ‘r+b’) #1306

  • Enhancement to AccessLogger (pass extra dict) #1303

  • Show more verbose message on import errors #1319

  • Added save and load functionality for CookieJar #1219

  • Added option on StaticRoute to follow symlinks #1299

  • Force encoding of application/json content type to utf-8 #1339

  • Fix invalid invocations of errors.LineTooLong #1335

  • Websockets: Stop async for iteration when connection is closed #1144

  • Ensure TestClient HTTP methods return a context manager #1318

  • Raise ClientDisconnectedError to FlowControlStreamReader read function if ClientSession object is closed by client when reading data. #1323

  • Document deployment without Gunicorn #1120

  • Add deprecation warning for MD5 and SHA1 digests when used for fingerprint of site certs in TCPConnector. #1186

  • Implement sub-applications #1301

  • Don’t inherit web.Request from dict but implement MutableMapping protocol.

  • Implement frozen signals

  • Don’t inherit web.Application from dict but implement MutableMapping protocol.

  • Support freezing for web applications

  • Accept access_log parameter in web.run_app, use None to disable logging

  • Don’t flap tcp_cork and tcp_nodelay in regular request handling. tcp_nodelay is still enabled by default.

  • Improve performance of web server by removing premature computing of Content-Type if the value was set by web.Response constructor.

    While the patch boosts speed of trivial web.Response(text=’OK’, content_type=’text/plain) very well please don’t expect significant boost of your application – a couple DB requests and business logic is still the main bottleneck.

  • Boost performance by adding a custom time service #1350

  • Extend ClientResponse with content_type and charset properties like in web.Request. #1349

  • Disable aiodns by default #559

  • Don’t flap tcp_cork in client code, use TCP_NODELAY mode by default.

  • Implement web.Request.clone() #1361

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