python - How can I await inside future-like object's __await__?

Question

PEP 0492 adds new __await__ magic method. Object that implements this method becomes future-like object and can be awaited using await. It's clear:

import asyncio


class Waiting:
    def __await__(self):
        yield from asyncio.sleep(2)
        print('ok')

async def main():
    await Waiting()

if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

Ok, but what if I want to call some async def defined function instead of asyncio.sleep? I can't use await because __await__ is not async function, I can't use yield from because native coroutines requires await expression:

async def new_sleep():
    await asyncio.sleep(2)

class Waiting:
    def __await__(self):
        yield from new_sleep()  # this is TypeError
        await new_sleep()  # this is SyntaxError
        print('ok')

How can I solve it?

question from:https://stackoverflow.com/questions/33409888/how-can-i-await-inside-future-like-objects-await

Answer 1

Use direct __await__() call:

async def new_sleep():
    await asyncio.sleep(2)

class Waiting:
    def __await__(self):
        return new_sleep().__await__()

The solution was recommended by Yury Selivanov (the author of PEP 492) for aioodbc library