This gist is sample code for a question posted on stackoverflow related to working of Future.set_result function in multi-threaded setting. https://stackoverflow.com/questions/57144657/unable-to-understand-behavior-of-future-set-result-on-futures-in-another-thread

future_set_result.py

import asyncio
import threading
from typing import Dict
import numpy as np
import time

# import logging
# logging.basicConfig(level=logging.DEBUG)


def read():
    delay = np.round(np.random.uniform(0.5, 1), 3)
    time.sleep(delay)
    choice = np.random.choice((3, 6, 9))
    # logging.debug("choice %d delay %f", choice, delay)
    return choice, delay


class RandomReader:
    def __init__(self):
        self.loop = asyncio.get_event_loop()
        self.service = 3
        self.thread = threading.Thread(target=self.reader)
        self.thread.start()
        self.futures: Dict[int, asyncio.Future] = {}

    def reader(self):
        while self.service != 0:
            k, v = read()
            if k in self.futures:
                if self.futures[k].done():
                    continue

                self.loop.call_soon_threadsafe(self.futures[k].set_result, v)
                self.service -= 1

    async def wait(self, v: int):
        self.futures[v] = self.loop.create_future()
        a = await self.futures[v]
        # logging.debug("value %d received %f", v, a)
        return v, a


async def main():
    reader = RandomReader()
    t1 = asyncio.create_task(reader.wait(3))
    print(await t1)
    t2 = asyncio.create_task(reader.wait(6))
    t3 = asyncio.create_task(reader.wait(9))
    print(await t2)
    print(await t3)
    reader.thread.join()


if __name__ == '__main__':
    loop_ = asyncio.get_event_loop()
    loop_.run_until_complete(main())