Idiomatically gather results from a dict of futures

Question

I'm trying to write something as idiomatic as possible to gather results from futures stored in a dict.

Let's imagine I have the following code:

import asyncio

async def sleep(seconds):
    print(f'sleeping for {seconds} seconds')
    await asyncio.sleep(seconds)
    print(f'finished sleeping {seconds} seconds')


async def run():
    tasks = {
        '4': sleep(4),
        '3': sleep(3),
        '2': sleep(2),
        '1': sleep(1),
    }
    print(await gather_from_dict(tasks))


if __name__ == '__main__':
     asyncio.get_event_loop().run_until_complete(run())

The output I'm expecting is:

sleeping for 2 seconds
sleeping for 1 seconds
sleeping for 4 seconds
sleeping for 3 seconds
finished sleeping 1 seconds
finished sleeping 2 seconds
finished sleeping 3 seconds
finished sleeping 4 seconds
{'4': None, '3': None, '2': None, '1': None}

So far the cleanest solution I've found is:

async def gather_from_dict(tasks:Dict[Hashable, Awaitable],
                           loop=None, return_exceptions=False) -> Dict:

    results = await asyncio.gather(
        *tasks.values(),
        loop=loop,
        return_exceptions=return_exceptions
    )
    return dict(zip(tasks.keys(), results))

Any ideas on how to do this in a simpler way? Thanks!!!

Answer 1

I redefined your tasks to make it purer as coroutine lists, and prefer to get the results from the run_until_complete methods, codes like the following, and notice that I return something in your sleep codes, in your codes, you actually return None.

import asyncio


async def sleep(seconds):
    print('sleeping for {seconds} seconds'.format(seconds=seconds))
    await asyncio.sleep(seconds)
    print('finished sleeping {seconds} seconds'.format(seconds=seconds))
    return {seconds: 'value of {seconds}'.format(seconds=seconds)}


if __name__ == '__main__':

    loop = asyncio.get_event_loop()

    tasks = [sleep(i) for i in range(1, 5)]

    finished, _ = loop.run_until_complete(
        asyncio.wait(tasks))

    result = {}

    for task in finished:
        result.update(task.result())

    print(result)
    loop.close()