import asyncio

async def factorial(name, number):
    f = 1
    for i in range(2, number+1):
        print("Task %s: Compute factorial(%s)..." % (name, i))
        f *= i
        await asyncio.sleep(1)
        print("Task %s: factorial(%s) = %s" % (name, number, f))
        yield f

async def collect_one_source(name, number):
    return [f async for f in factorial(name, number)]

async def collect_everything():
    futures = [
        collect_one_source("A", 2),
        collect_one_source("B", 3),
        collect_one_source("C", 4),
    ]
    result = [
        await future
        for future in asyncio.as_completed(futures)
    ]
    result.sort()
    return result

loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.gather(
    factorial("A", 2),
    factorial("B", 3),
    factorial("C", 4),
))
loop.close()