learn_asyncio/real_python

Real Python AsyncIO Walkthrough

https://realpython.com/async-io-python/

Rules of Async Coroutines

async def f(x):
    y = await z(x)  # OK - `await` and `return` allowed in coroutines
    return y

async def g(x):
    yield x  # OK - this is an async generator

async def m(x):
    yield from gen(x)  # No - SyntaxError

def m(x):
    y = await z(x)  # Still no - SyntaxError (no `async def` here)
    return y

An awaitable object is either (1) another coroutine or (2) an object defining an .await() dunder method that returns an iterator.