Opening a network connection takes waiting, and so does closing it. async with is with for resources whose setup and cleanup need await. An object supports it by defining async def __aenter__ and async def __aexit__.

The short form mirrors contextmanager:

import asyncio
from contextlib import asynccontextmanager

@asynccontextmanager
async def connection(name):
    await asyncio.sleep(0.01)  # connect
    print("open", name)
    try:
        yield name.upper()
    finally:
        await asyncio.sleep(0.01)  # close
        print("closed", name)

async def main():
    async with connection("db") as conn:
        print("using", conn)

asyncio.run(main())

Code before yield is the setup, and the yielded value is what as receives. An exception in the block, cancellation included, is raised at the yield, so a try around it decides which cleanup always happens.

Write an async context manager transaction(db) that awaits db.begin() on entry and gives the block db. When the block finishes, await db.commit(); when it raises or is cancelled, await db.rollback() instead and let the exception continue.

The explanation opens here once every check passes.