Async http client/server framework

Key Features

• Supports both client and server side of HTTP protocol.
• Supports both client and server Web-Sockets out-of-the-box and avoids Callback Hell.
• Provides Web-server with middlewares and plugable routing.

Getting started

Client

To get something from the web:

import aiohttp
import asyncio

async def main():

    async with aiohttp.ClientSession() as session:
        async with session.get('http://python.org') as response:

            print("Status:", response.status)
            print("Content-type:", response.headers['content-type'])

            html = await response.text()
            print("Body:", html[:15], "...")

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

This prints:

Status: 200
Content-type: text/html; charset=utf-8
Body:  ...

Coming from requests ? Read why we need so many lines.

Server

An example using a simple server:

# examples/server_simple.py
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(msg.data))
        elif msg.type == web.WSMsgType.binary:
            await ws.send_bytes(msg.data)
        elif msg.type == web.WSMsgType.close:
            break

    return ws


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

if __name__ == '__main__':
    web.run_app(app)

Documentation

Demos

External links

• Third party libraries
• Built with aiohttp
• Powered by aiohttp

Feel free to make a Pull Request for adding your link to these pages!

Communication channels

aio-libs discourse group:

gitter chat

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

Requirements

• Python >= 3.6
• async-timeout
• attrs
• chardet
• multidict
• yarl

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

License

aiohttp is offered under the Apache 2 license.

Keepsafe

The aiohttp community would like to thank Keepsafe () for its support in the early days of the project.

Source code

The latest developer version is available in a GitHub repository:

Benchmarks

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

Changelog

3.7.4.post0 (2021-03-06)

Misc

• Bumped upper bound of the chardet runtime dependency to allow their v4.0 version stream. #5366

---

3.7.4 (2021-02-25)

Bugfixes

• (SECURITY BUG) Started preventing open redirects in the aiohttp.web.normalize_path_middleware middleware. For more details, see .

  Thanks to Beast Glatisant for finding the first instance of this issue and Jelmer Vernooij for reporting and tracking it down in aiohttp. #5497

• Fix interpretation difference of the pure-Python and the Cython-based HTTP parsers construct a yarl.URL object for HTTP request-target.

  Before this fix, the Python parser would turn the URI's absolute-path for //some-path into / while the Cython code preserved it as //some-path. Now, both do the latter. #5498

---

3.7.3 (2020-11-18)

Features

• Use Brotli instead of brotlipy #3803
• Made exceptions pickleable. Also changed the repr of some exceptions. #4077

Bugfixes

• Raise a ClientResponseError instead of an AssertionError for a blank HTTP Reason Phrase. #3532
• Fix web_middlewares.normalize_path_middleware behavior for patch without slash. #3669
• Fix overshadowing of overlapped sub-applications prefixes. #3701
• Make BaseConnector.close() a coroutine and wait until the client closes all connections. Drop deprecated "with Connector():" syntax. #3736
• Reset the sock_read timeout each time data is received for a aiohttp.client response. #3808
• Fixed type annotation for add_view method of UrlDispatcher to accept any subclass of View #3880
• Fixed querying the address families from DNS that the current host supports. #5156
• Change return type of MultipartReader.__aiter__() and BodyPartReader.__aiter__() to AsyncIterator. #5163
• Provide x86 Windows wheels. #5230

Improved Documentation

• Add documentation for aiohttp.web.FileResponse. #3958
• Removed deprecation warning in tracing example docs #3964
• Fixed wrong "Usage" docstring of aiohttp.client.request. #4603
• Add aiohttp-pydantic to third party libraries #5228

Misc

• #4102

---

3.7.2 (2020-10-27)

Bugfixes

• Fixed static files handling for loops without .sendfile() support #5149

---

3.7.1 (2020-10-25)

Bugfixes

• Fixed a type error caused by the conditional import of Protocol. #5111
• Server doesn't send Content-Length for 1xx or 204 #4901
• Fix run_app typing #4957
• Always require typing_extensions library. #5107
• Fix a variable-shadowing bug causing ThreadedResolver.resolve to return the resolved IP as the hostname in each record, which prevented validation of HTTPS connections. #5110
• Added annotations to all public attributes. #5115
• Fix flaky test_when_timeout_smaller_second #5116
• Ensure sending a zero byte file does not throw an exception #5124
• Fix a bug in web.run_app() about Python version checking on Windows #5127

---

3.7.0 (2020-10-24)

Features

• Response headers are now prepared prior to running on_response_prepare hooks, directly before headers are sent to the client. #1958
• Add a quote_cookie option to CookieJar, a way to skip quotation wrapping of cookies containing special characters. #2571
• Call AccessLogger.log with the current exception available from sys.exc_info(). #3557
• web.UrlDispatcher.add_routes and web.Application.add_routes return a list of registered AbstractRoute instances. AbstractRouteDef.register (and all subclasses) return a list of registered resources registered resource. #3866
• Added properties of default ClientSession params to ClientSession class so it is available for introspection #3882
• Don't cancel web handler on peer disconnection, raise OSError on reading/writing instead. #4080
• Implement BaseRequest.get_extra_info() to access a protocol transports' extra info. #4189
• Added ClientSession.timeout property. #4191
• allow use of SameSite in cookies. #4224
• Use loop.sendfile() instead of custom implementation if available. #4269
• Apply SO_REUSEADDR to test server's socket. #4393
• Use .raw_host instead of slower .host in client API #4402
• Allow configuring the buffer size of input stream by passing read_bufsize argument. #4453
• Pass tests on Python 3.8 for Windows. #4513
• Add method and url attributes to TraceRequestChunkSentParams and TraceResponseChunkReceivedParams. #4674
• Add ClientResponse.ok property for checking status code under 400. #4711
• Don't ceil timeouts that are smaller than 5 seconds. #4850
• TCPSite now listens by default on all interfaces instead of just IPv4 when None is passed in as the host. #4894
• Bump http_parser to 2.9.4 #5070

Bugfixes

• Fix keepalive connections not being closed in time #3296

• Fix failed websocket handshake leaving connection hanging. #3380

• Fix tasks cancellation order on exit. The run_app task needs to be cancelled first for cleanup hooks to run with all tasks intact. #3805

• Don't start heartbeat until _writer is set #4062

• Fix handling of multipart file uploads without a content type. #4089

• Preserve view handler function attributes across middlewares #4174

• Fix the string representation of ServerDisconnectedError. #4175

• Raising RuntimeError when trying to get encoding from not read body #4214

• Remove warning messages from noop. #4282

• Raise ClientPayloadError if FormData re-processed. #4345

• Fix a warning about unfinished task in web_protocol.py #4408

• Fixed 'deflate' compression. According to RFC 2616 now. #4506

• Fixed OverflowError on platforms with 32-bit time_t #4515

• Fixed request.body_exists returns wrong value for methods without body. #4528

• Fix connecting to link-local IPv6 addresses. #4554

• Fix a problem with connection waiters that are never awaited. #4562

• Always make sure transport is not closing before reuse a connection.

  Reuse a protocol based on keepalive in headers is unreliable. For example, uWSGI will not support keepalive even it serves a HTTP 1.1 request, except explicitly configure uWSGI with a --http-keepalive option.

  Servers designed like uWSGI could cause aiohttp intermittently raise a ConnectionResetException when the protocol poll runs out and some protocol is reused. #4587

• Handle the last CRLF correctly even if it is received via separate TCP segment. #4630

• Fix the register_resource function to validate route name before splitting it so that route name can include python keywords. #4691

• Improve typing annotations for web.Request, aiohttp.ClientResponse and multipart module. #4736

• Fix resolver task is not awaited when connector is cancelled #4795

• Fix a bug "Aiohttp doesn't return any error on invalid request methods" #4798

• Fix HEAD requests for static content. #4809

• Fix incorrect size calculation for memoryview #4890

• Add HTTPMove to _all__. #4897

• Fixed the type annotations in the tracing module. #4912

• Fix typing for multipart __aiter__. #4931

• Fix for race condition on connections in BaseConnector that leads to exceeding the connection limit. #4936

• Add forced UTF-8 encoding for application/rdap+json responses. #4938

• Fix inconsistency between Python and C http request parsers in parsing pct-encoded URL. #4972

• Fix connection closing issue in HEAD request. #5012

• Fix type hint on BaseRunner.addresses (from List[str] to List[Any]) #5086

• Make web.run_app() more responsive to Ctrl+C on Windows for Python < 3.8. It slightly increases CPU load as a side effect. #5098

Improved Documentation

• Fix example code in client quick-start #3376
• Updated the docs so there is no contradiction in ttl_dns_cache default value #3512
• Add 'Deploy with SSL' to docs. #4201
• Change typing of the secure argument on StreamResponse.set_cookie from Optional[str] to Optional[bool] #4204
• Changes ttl_dns_cache type from int to Optional[int]. #4270
• Simplify README hello word example and add a documentation page for people coming from requests. #4272
• Improve some code examples in the documentation involving websockets and starting a simple HTTP site with an AppRunner. #4285
• Fix typo in code example in Multipart docs #4312
• Fix code example in Multipart section. #4314
• Update contributing guide so new contributors read the most recent version of that guide. Update command used to create test coverage reporting. #4810
• Spelling: Change "canonize" to "canonicalize". #4986
• Add aiohttp-sse-client library to third party usage list. #5084

Misc

• #2856, #4218, #4250

---

3.6.3 (2020-10-12)

Bugfixes

• Pin yarl to <1.6.0 to avoid buggy behavior that will be fixed by the next aiohttp release.

3.6.2 (2019-10-09)

Features

• Made exceptions pickleable. Also changed the repr of some exceptions. #4077
• Use Iterable type hint instead of Sequence for Application middleware parameter. #4125

Bugfixes

• Reset the sock_read timeout each time data is received for a aiohttp.ClientResponse. #3808
• Fix handling of expired cookies so they are not stored in CookieJar. #4063
• Fix misleading message in the string representation of ClientConnectorError; self.ssl == None means default SSL context, not SSL disabled #4097
• Don't clobber HTTP status when using FileResponse. #4106

Improved Documentation

• Added minimal required logging configuration to logging documentation. #2469
• Update docs to reflect proxy support. #4100
• Fix typo in code example in testing docs. #4108

Misc

• #4102

---

3.6.1 (2019-09-19)

Features

• Compatibility with Python 3.8. #4056

Bugfixes

• correct some exception string format #4068
• Emit a warning when ssl.OP_NO_COMPRESSION is unavailable because the runtime is built against an outdated OpenSSL. #4052
• Update multidict requirement to >= 4.5 #4057

Improved Documentation

• Provide pytest-aiohttp namespace for pytest fixtures in docs. #3723

---

3.6.0 (2019-09-06)

Features

• Add support for Named Pipes (Site and Connector) under Windows. This feature requires Proactor event loop to work. #3629
• Removed Transfer-Encoding: chunked header from websocket responses to be compatible with more http proxy servers. #3798
• Accept non-GET request for starting websocket handshake on server side. #3980

Bugfixes

• Raise a ClientResponseError instead of an AssertionError for a blank HTTP Reason Phrase. #3532

• Fix an issue where cookies would sometimes not be set during a redirect. #3576

• Change normalize_path_middleware to use 308 redirect instead of 301.

  This behavior should prevent clients from being unable to use PUT/POST methods on endpoints that are redirected because of a trailing slash. #3579

• Drop the processed task from all_tasks() list early. It prevents logging about a task with unhandled exception when the server is used in conjunction with asyncio.run(). #3587

• Signal type annotation changed from Signal[Callable[['TraceConfig'], Awaitable[None]]] to Signal[Callable[ClientSession, SimpleNamespace, ...]. #3595

• Use sanitized URL as Location header in redirects #3614

• Improve typing annotations for multipart.py along with changes required by mypy in files that references multipart.py. #3621

• Close session created inside aiohttp.request when unhandled exception occurs #3628

• Cleanup per-chunk data in generic data read. Memory leak fixed. #3631

• Use correct type for add_view and family #3633

• Fix _keepalive field in __slots__ of RequestHandler. #3644

• Properly handle ConnectionResetError, to silence the "Cannot write to closing transport" exception when clients disconnect uncleanly. #3648

• Suppress pytest warnings due to test_utils classes #3660

• Fix overshadowing of overlapped sub-application prefixes. #3701

• Fixed return type annotation for WSMessage.json() #3720

• Properly expose TooManyRedirects publicly as documented. #3818

• Fix missing brackets for IPv6 in proxy CONNECT request #3841

• Make the signature of aiohttp.test_utils.TestClient.request match asyncio.ClientSession.request according to the docs #3852

• Use correct style for re-exported imports, makes mypy --strict mode happy. #3868

• Fixed type annotation for add_view method of UrlDispatcher to accept any subclass of View #3880

• Made cython HTTP parser set Reason-Phrase of the response to an empty string if it is missing. #3906

• Add URL to the string representation of ClientResponseError. #3959

• Accept istr keys in LooseHeaders type hints. #3976

• Fixed race conditions in _resolve_host caching and throttling when tracing is enabled. #4013

• For URLs like "unix://localhost/..." set Host HTTP header to "localhost" instead of "localhost:None". #4039

Improved Documentation

• Modify documentation for Background Tasks to remove deprecated usage of event loop. #3526
• use if __name__ == '__main__': in server examples. #3775
• Update documentation reference to the default access logger. #3783
• Improve documentation for web.BaseRequest.path and web.BaseRequest.raw_path. #3791
• Removed deprecation warning in tracing example docs #3964

---

3.5.4 (2019-01-12)

Bugfixes

• Fix stream .read() / .readany() / .iter_any() which used to return a partial content only in case of compressed content #3525

3.5.3 (2019-01-10)

Bugfixes

• Fix type stubs for aiohttp.web.run_app(access_log=True) and fix edge case of access_log=True and the event loop being in debug mode. #3504
• Fix aiohttp.ClientTimeout type annotations to accept None for fields #3511
• Send custom per-request cookies even if session jar is empty #3515
• Restore Linux binary wheels publishing on PyPI

---

3.5.2 (2019-01-08)

Features

• FileResponse from web_fileresponse.py uses a ThreadPoolExecutor to work with files asynchronously. I/O based payloads from payload.py uses a ThreadPoolExecutor to work with I/O objects asynchronously. #3313
• Internal Server Errors in plain text if the browser does not support HTML. #3483

Bugfixes

• Preserve MultipartWriter parts headers on write. Refactor the way how Payload.headers are handled. Payload instances now always have headers and Content-Type defined. Fix Payload Content-Disposition header reset after initial creation. #3035
• Log suppressed exceptions in GunicornWebWorker. #3464
• Remove wildcard imports. #3468
• Use the same task for app initialization and web server handling in gunicorn workers. It allows to use Python3.7 context vars smoothly. #3471
• Fix handling of chunked+gzipped response when first chunk does not give uncompressed data #3477
• Replace collections.MutableMapping with collections.abc.MutableMapping to avoid a deprecation warning. #3480
• Payload.size type annotation changed from Optional[float] to Optional[int]. #3484
• Ignore done tasks when cancels pending activities on web.run_app finalization. #3497

Improved Documentation

• Add documentation for aiohttp.web.HTTPException. #3490

Misc

• #3487

---

3.5.1 (2018-12-24)

• Fix a regression about ClientSession._requote_redirect_url modification in debug mode.

3.5.0 (2018-12-22)

Features

• The library type annotations are checked in strict mode now.
• Add support for setting cookies for individual request (#2387)
• Application.add_domain implementation (#2809)
• The default app in the request returned by test_utils.make_mocked_request can now have objects assigned to it and retrieved using the [] operator. (#3174)
• Make request.url accessible when transport is closed. (#3177)
• Add zlib_executor_size argument to Response constructor to allow compression to run in a background executor to avoid blocking the main thread and potentially triggering health check failures. (#3205)
• Enable users to set ClientTimeout in aiohttp.request (#3213)
• Don't raise a warning if NETRC environment variable is not set and ~/.netrc file doesn't exist. (#3267)
• Add default logging handler to web.run_app If the Application.debug flag is set and the default logger aiohttp.access is used, access logs will now be output using a *stderr* StreamHandler if no handlers are attached. Furthermore, if the default logger has no log level set, the log level will be set to DEBUG. (#3324 <>`_)
• Add method argument to session.ws_connect(). Sometimes server API requires a different HTTP method for WebSocket connection establishment. For example, Docker exec needs POST. (#3378)
• Create a task per request handling. (#3406)

Bugfixes

• Enable passing access_log_class via handler_args (#3158)
• Return empty bytes with end-of-chunk marker in empty stream reader. (#3186)
• Accept CIMultiDictProxy instances for headers argument in web.Response constructor. (#3207)
• Don't uppercase HTTP method in parser (#3233)
• Make method match regexp RFC-7230 compliant (#3235)
• Add app.pre_frozen state to properly handle startup signals in sub-applications. (#3237)
• Enhanced parsing and validation of helpers.BasicAuth.decode. (#3239)
• Change imports from collections module in preparation for 3.8. (#3258)
• Ensure Host header is added first to ClientRequest to better replicate browser (#3265)
• Fix forward compatibility with Python 3.8: importing ABCs directly from the collections module will not be supported anymore. (#3273)
• Keep the query string by normalize_path_middleware. (#3278)
• Fix missing parameter raise_for_status for aiohttp.request() (#3290)
• Bracket IPv6 addresses in the HOST header (#3304)
• Fix default message for server ping and pong frames. (#3308)
• Fix tests/test_connector.py typo and tests/autobahn/server.py duplicate loop def. (#3337)
• Fix false-negative indicator end_of_HTTP_chunk in StreamReader.readchunk function (#3361)
• Release HTTP response before raising status exception (#3364)
• Fix task cancellation when sendfile() syscall is used by static file handling. (#3383)
• Fix stack trace for asyncio.TimeoutError which was not logged, when it is caught in the handler. (#3414)

Improved Documentation

• Improve documentation of Application.make_handler parameters. (#3152)
• Fix BaseRequest.raw_headers doc. (#3215)
• Fix typo in TypeError exception reason in web.Application._handle (#3229)
• Make server access log format placeholder %b documentation reflect behavior and docstring. (#3307)

Deprecations and Removals

• Deprecate modification of session.requote_redirect_url (#2278)
• Deprecate stream.unread_data() (#3260)
• Deprecated use of boolean in resp.enable_compression() (#3318)
• Encourage creation of aiohttp public objects inside a coroutine (#3331)
• Drop dead Connection.detach() and Connection.writer. Both methods were broken for more than 2 years. (#3358)
• Deprecate app.loop, request.loop, client.loop and connector.loop properties. (#3374)
• Deprecate explicit debug argument. Use asyncio debug mode instead. (#3381)
• Deprecate body parameter in HTTPException (and derived classes) constructor. (#3385)
• Deprecate bare connector close, use async with connector: and await connector.close() instead. (#3417)
• Deprecate obsolete read_timeout and conn_timeout in ClientSession constructor. (#3438)

Misc

• #3341, #3351