Python 3.8.3 : About aiohttp python package.

This python package can help you to writing single-threaded concurrent code using coroutines, multiplexing I/O access over sockets and other resources, running network clients and servers, and other related primitives, see the official documentation.
In this simple tutorial, I will show you in a few simple steps how to use it.
It is a complex module and there are multiple ways to use it.
First, on the Windows operating system users can install easily with:

pip3 install aiohttp
Collecting aiohttp
...
Installing collected packages: attrs, multidict, yarl, async-timeout, aiohttp
Successfully installed aiohttp-3.6.2 async-timeout-3.0.1 attrs-19.3.0 multidict-4.7.6 yarl-1.4.2

If you use a Linus operating system then you can use this command:

[mythcat@desk ~]$ pip3 install aiohttp --user 
...
Successfully installed aiohttp-3.6.2 async-timeout-3.0.1 multidict-4.7.5 yarl-1.4.2

This python package can be used as client or server.
The aiohttp.web implements a basic CLI for quickly serving an Application in development over TCP/IP.
You can find some example on this webpage.
These simple examples show how you can use handlers for web and servers and a request handler with a coroutine.

[mythcat@desk ~]$ python3 
Python 3.7.6 (default, Jan 30 2020, 09:44:41) 
[GCC 9.2.1 20190827 (Red Hat 9.2.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from aiohttp import web 
>>> def handler_req(request):
...     return web.Response(text='Handler')
... 
>>> handler_req
<function 0x7fc8a76aab00="" at="" handler_req="">
>>> async def handler_req_async(request):
...     return web.Response(text='async Handler')
... 
>>> handler_req_async
<function+0x7fc8a574edd0...
>>> import aiohttp
>>> from aiohttp import web
>>> from aiohttp.client import _RequestContextManager
>>> async def test_await(test_server, loop):
...  
...     async def handler(request):
...         return web.HTTPOk()
...
...     app = web.Application(loop=loop)
...     app.router.add_route('GET', '/', handler)
...     server = await test_server(app)
...     resp = await aiohttp.get(server.make_url('/'), loop=loop)
...     assert resp.status == 200
...     assert resp.connection is not None
...     await resp.release()
...     assert resp.connection is None
>>> test_await('htthttp://localhost:8080/',1000)   
<coroutine object test_await at 0x00000261FB96EA40>

Let's see the output of the dir:

dir(aiohttp)
['AsyncIterablePayload', 'AsyncResolver', 'BadContentDispositionHeader', 'BadContentDispositionParam', 
'BaseConnector', 'BasicAuth', 'BodyPartReader', 'BufferedReaderPayload', 'BytesIOPayload', 'BytesPayload',
 'ChainMapProxy', 'ClientConnectionError', 'ClientConnectorCertificateError', 'ClientConnectorError', 
'ClientConnectorSSLError', 'ClientError', 'ClientHttpProxyError', 'ClientOSError', 'ClientPayloadError', 
'ClientProxyConnectionError', 'ClientRequest', 'ClientResponse', 'ClientResponseError', 'ClientSSLError', 
'ClientSession', 'ClientTimeout', 'ClientWebSocketResponse', 'ContentTypeError', 'CookieJar', 'DataQueue', 
'DefaultResolver', 'DummyCookieJar', 'EMPTY_PAYLOAD', 'EofStream', 'Fingerprint', 'FlowControlDataQueue', 
'FormData', 'HttpVersion', 'HttpVersion10', 'HttpVersion11', 'IOBasePayload', 'InvalidURL', 'JsonPayload', 
'MultipartReader', 'MultipartWriter', 'NamedPipeConnector', 'PAYLOAD_REGISTRY', 'Payload', 'RequestInfo', 
'ServerConnectionError', 'ServerDisconnectedError', 'ServerFingerprintMismatch', 'ServerTimeoutError', 
'Signal', 'StreamReader', 'StringIOPayload', 'StringPayload', 'TCPConnector', 'TextIOPayload', 
'ThreadedResolver', 'TooManyRedirects', 'TraceConfig', 'TraceConnectionCreateEndParams', 
'TraceConnectionCreateStartParams', 'TraceConnectionQueuedEndParams', 'TraceConnectionQueuedStartParams', 
'TraceConnectionReuseconnParams', 'TraceDnsCacheHitParams', 'TraceDnsCacheMissParams', 
'TraceDnsResolveHostEndParams', 'TraceDnsResolveHostStartParams', 'TraceRequestChunkSentParams', 
'TraceRequestEndParams', 'TraceRequestExceptionParams', 'TraceRequestRedirectParams', 'TraceRequestStartParams',
 'TraceResponseChunkReceivedParams', 'Tuple', 'UnixConnector', 'WSCloseCode', 'WSMessage', 'WSMsgType', 
'WSServerHandshakeError', 'WebSocketError', '__all__', '__builtins__', '__cached__', '__doc__', '__file__',
 '__loader__', '__name__', '__package__', '__path__', '__spec__', '__version__', 'abc', 'base_protocol', 
'client', 'client_exceptions', 'client_proto', 'client_reqrep', 'client_ws', 'connector', 
'content_disposition_filename', 'cookiejar', 'formdata', 'frozenlist', 'get_payload', 'hdrs', 'helpers', 
'http', 'http_exceptions', 'http_parser', 'http_websocket', 'http_writer', 'locks', 'log', 'multipart', 
'parse_content_disposition', 'payload', 'payload_streamer', 'payload_type', 'request', 'resolver', 'signals', 
'streamer', 'streams', 'tcp_helpers', 'tracing', 'typedefs']