Equivalent of asyncio.Queues with worker “threads”

Question

I\'m trying to figure out how to port a threaded program to use asyncio. I have a lot of code which synchronizes around a few standard library Queues, basically like this: <

Answer 1

Yes, exactly. Tasks are your friends:

import asyncio, random

q = asyncio.Queue()

@asyncio.coroutine
def produce():
    while True:
        yield from q.put(random.random())
        yield from asyncio.sleep(0.5 + random.random())

@asyncio.coroutine
def consume():
    while True:
        value = yield from q.get()
        print("Consumed", value)


loop = asyncio.get_event_loop()
loop.create_task(produce())
loop.create_task(consume())
loop.run_forever()

asyncio.ensure_future can be used for task creation also.

And please keep in mind: q.put() is a coroutine, so you should to use yield from q.put(value).

UPD

Switched from asyncio.Task()/asyncio.async() to new brand API loop.create_task() and asyncio.ensure_future() in example.

Answer 2

A bit later and maybe OT, have in mind that you can consume from the Queue from multiple tasks as they were independent consumers.

The following snippet shows as an example how you can achieve the same thread pool pattern with asyncio tasks.

q = asyncio.Queue()

async def sum(x):
    await asyncio.sleep(0.1)  # simulates asynchronously
    return x

async def consumer(i):
    print("Consumer {} started".format(i))
    while True:
        f, x = await q.get()
        print("Consumer {} procesing {}".format(i, x))
        r = await sum(x)
        f.set_result(r)

async def producer():
    consumers = [asyncio.ensure_future(consumer(i)) for i in range(5)]
    loop = asyncio.get_event_loop()
    tasks = [(asyncio.Future(), x) for x in range(10)]
    for task in tasks:
        await q.put(task)

    # wait until all futures are completed
    results = await asyncio.gather(*[f for f, _ in tasks])
    assert results == [r for _, r in tasks]

    # destroy tasks
    for c in consumers:
        c.cancel()


asyncio.get_event_loop().run_until_complete(producer())

Answer 3

Here's what I use in production, moved to gist: https://gist.github.com/thehesiod/7081ab165b9a0d4de2e07d321cc2391d