Python asyncio - 如何懒惰地链接（）从 as_completed() 返回的结果？

Question

在下面的代码示例中，我需要为第 3 步找到解决方案):

import asyncio as aio
import random


async def produce_numbers(x):
    await aio.sleep(random.uniform(0, 3.0))
    return [x * x, x * x + 1, x * x + 2]


async def main():

    # Step 1) Create a list of unawaited coroutines.
    coros = [produce_numbers(i) for i in range(0, 10)]

    # Step 2) Create generator to return items in order of completion.
    futs = aio.as_completed(coros)  # type: generator

    # Step 3) Create a generator that returns every single number lazily.
    # This is the step I don't know how to accomplish.
    # I can't find a way to chain the lists that I get from each
    # `produce_numbers()` call together in a lazy manner.

    # Step 4) This loops should fire as soon as the first
    # `produce_numbers()` coroutine finished.
    for number in my_number_generator:
        print(number)


if __name__ == '__main__':
    loop = aio.get_event_loop()
    loop.run_until_complete(main())

也许我缺少标准库中的一个关键函数？

Answer 1

asyncio.as_completed() 产生期货，您需要等待每个期货才能获得列表结果。您可以使用带有双循环的异步生成器表达式来展平它们：

flattened = (v for fut in futs for v in await fut)

async for number in flattened:
    print(number)

或者使用单独的异步生成器函数来使用完整语句进行循环：

async def flatten_futures(futures):
    for future in futures:
        for value in await future:
            yield value

并在 main() 中用作

async for number in flatten_futures(futs):
    print(number)

Python asyncio - 如何懒惰地链接（）从 as_completed() 返回的结果？

Python asyncio - How to chain() the results returned from as_completed() lazily?

python

generator

python-asyncio