chaining asyncio

chain.py

import asyncio


async def poopyface(value):
    if value == 3:
        raise RuntimeError('Bail')
    print(value)


def runall(*awaitables, loop=None):
    if not loop:
        loop = asyncio.get_event_loop()

    outer = loop. create_future()
    tasks = iter(awaitables)

    def chain_next_task(result):
        exc = result.exception()
        if exc:
            for pending_task in tasks:
                future = asyncio.ensure_future(pending_task)
                future._log_destroy_pending = False
                future.cancel()
            outer.set_exception(exc)
        else:
            try:
                future = asyncio.ensure_future(next(tasks))
                future._log_destroy_pending = False
                future.add_done_callback(chain_next_task)
            except StopIteration:
                outer.set_result(result.done())

    future = asyncio.ensure_future(next(tasks))
    future.add_done_callback(chain_next_task)
    return outer


loop = asyncio.get_event_loop()
loop.run_until_complete(runall(poopyface(1), poopyface(2), poopyface(3)))