future, async, await 에서 여러 future 를 실행하고 작업이 끝날 때까지 대기하는 방법

import asyncio


loop = asyncio.get_event_loop()
async def test(number):
    print(number)

async def main():

    futures = []
    for i in range(20):
        future = test(i)
        futures.append(future)

    print("future count : " + str(len(futures)))
    (done, pending) = await asyncio.wait(futures)
    if pending:
        print("there is {} tasks not completed".format(len(pending)))
        for f in pending:
            f.cancel()
    for f in done:
        ret = await f
        if ret is not None:
            print(ret)

loop.run_until_complete(main())