How to use thread in asyncio?

Question

I want to new a thread to do a io task with consumer/producer pattern in a asyncio task:

import asyncio
import threading
import time
import queue


q = queue.Queue()


def consumer():
    while True:
        v = q.get()
        time.sleep(v)
        print(f"log {v}")


async def work(v):
    await asyncio.sleep(0.1)
    print(f"work {v}")


async def main():
    t = threading.Thread(target=consumer, daemon=True)
    t.start()
    for i in range(1, 5):
        print(f"start {i}")
        q.put(i)
        loop.create_task(work(i))
        print(f"done {i}")
    t.join()


loop = asyncio.get_event_loop()
loop.run_until_complete(main())
loop.run_forever()

But the asyncio task cannot be execute because of consumer thread.

Answer 1

Instead of explicitly managing the worker thread and a queue, you can use the thread pool built into asyncio (or create your own if you wish) and call run_in_executor to submit tasks to it. For example:

import asyncio, time

def blocking_work(v):
    # this function is not async, it will be run in a separate thread
    time.sleep(v)
    print(f"log {v}")

async def work(v):
    # native asyncio work
    await asyncio.sleep(0.1)
    # followed by blocking IO wrapped in thread
    loop = asyncio.get_event_loop()
    await loop.run_in_executor(None, blocking_work, v)
    print(f"work {v}")

async def main():
    await asyncio.gather(*[work(i) for i in range(1, 5)])

asyncio.run(main())