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Async http client/server framework (asyncio)

Project description

Async http client/server framework

aiohttp logo

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Key Features

  • Supports both client and server side of HTTP protocol.

  • Supports both client and server Web-Sockets out-of-the-box without the Callback Hell.

  • Web-server has middlewares and pluggable routing.

Getting started


To retrieve something from the web:

import aiohttp
import asyncio

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

async def main():
    async with aiohttp.ClientSession() 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 wshandle(request):
    ws = web.WebSocketResponse()
    await ws.prepare(request)

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

    return ws

app = web.Application()
app.add_routes([web.get('/', handle),
                web.get('/echo', wshandle),
                web.get('/{name}', handle)])




Communication channels

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

Feel free to post your questions and ideas here.

gitter chat

We support Stack Overflow. Please add aiohttp tag to your question there.


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:


3.4.1 (2018-08-28)

  • Fix empty header parsing regression. (#3218)

  • Fix BaseRequest.raw_headers doc. (#3215)

  • Fix documentation building on ReadTheDocs (#3221)

3.4.0 (2018-08-25)


  • Add type hints (#3049)

  • Add raise_for_status request parameter (#3073)

  • Add type hints to HTTP client (#3092)

  • Minor server optimizations (#3095)

  • Preserve the cause when HTTPException is raised from another exception. (#3096)

  • Add close_boundary option in MultipartWriter.write method. Support streaming (#3104)

  • Added a remove_slash option to the normalize_path_middleware factory. (#3173)

  • The class AbstractRouteDef is importable from aiohttp.web. (#3183)


  • Prevent double closing when client connection is released before the last data_received() callback. (#3031)

  • Make redirect with normalize_path_middleware work when using url encoded paths. (#3051)

  • Postpone web task creation to connection establishment. (#3052)

  • Fix sock_read timeout. (#3053)

  • When using a server-request body as the data= argument of a client request, iterate over the content with readany instead of readline to avoid Line too long errors. (#3054)

  • fix UrlDispatcher has no attribute add_options, add web.options (#3062)

  • correct filename in content-disposition with multipart body (#3064)

  • Many HTTP proxies has buggy keepalive support. Let’s not reuse connection but close it after processing every response. (#3070)

  • raise 413 “Payload Too Large” rather than raising ValueError in Add helpful debug message to 413 responses (#3087)

  • Fix StreamResponse equality, now that they are MutableMapping objects. (#3100)

  • Fix server request objects comparison (#3116)

  • Do not hang on 206 Partial Content response with Content-Encoding: gzip (#3123)

  • Fix timeout precondition checkers (#3145)

Improved Documentation

  • Add a new FAQ entry that clarifies that you should not reuse response objects in middleware functions. (#3020)

  • Add FAQ section “Why is creating a ClientSession outside of an event loop dangerous?” (#3072)

  • Fix link to Rambler (#3115)

  • Fix TCPSite documentation on the Server Reference page. (#3146)

  • Fix documentation build configuration file for Windows. (#3147)

  • Remove no longer existing lingering_timeout parameter of Application.make_handler from documentation. (#3151)

  • Mention that app.make_handler is deprecated, recommend to use runners API instead. (#3157)

Deprecations and Removals

  • Drop loop.current_task() from helpers.current_task() (#2826)

  • Drop reader parameter from request.multipart(). (#3090)

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