How to pass additional parameters to handle_client coroutine?

Question

The recommended way to use asyncio for a socket server is:

import asyncio

async def handle_client(reader, writer):
    request = (await reader.read(100)).de         


        

Answer 1

You can use a temporary function or a lambda:

async def main():
    session = aiohttp.ClientSession()
    await asyncio.start_server(lambda r, w: handle_client(r, w, session),
                               '', 55555)

This works because even though the lambda is not technically a coroutine, it behaves just like one - when invoked it returns a coroutine object.

For larger programs you might prefer a class-based approach where a class encapsulates the state shared by multiple clients without having to pass it explicitly. For example:

class ClientContext:
    def __init__(self):
        self.session = aiohttp.ClientSession()
        # ... add anything else you will need "globally"

    async def handle_client(self, reader, writer):
        # ... here you get reader and writer, but also have
        # session etc as self.session ...

async def main():
    ctx = ClientContext()
    await asyncio.start_server(ctx.handle_client), '', 55555)