我如何在类似未来的对象的__await__中等待? [英] How can I await inside future-like object's __await__?

问题描述

PEP 0492 添加了新的__await__魔术方法.实现此方法的对象将成为将来的对象，可以使用await等待.很明显:

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())

好，但是如果我想调用某些async def定义的函数而不是asyncio.sleep怎么办?我不能使用await，因为__await__不是async函数，我不能使用yield from，因为原生协程需要await表达式:

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')

我该如何解决?

推荐答案

使用直接__await__()调用:

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

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

该解决方案由Yury Selivanov( PEP 492 的作者)推荐用于 aioodbc库

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

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