Awaiting async code from sync

sync_await.py

import asyncio
import threading
from typing import Any, Awaitable, Iterable, Optional, TypeVar

T = TypeVar("T")


class sync_await:
    def __enter__(self) -> "sync_await":
        self._loop = asyncio.new_event_loop()
        self._looper = threading.Thread(target=self._loop.run_forever, daemon=True)
        self._looper.start()
        return self

    def __call__(self, coro: Awaitable[T], timeout: Optional[float] = None) -> T:
        return asyncio.run_coroutine_threadsafe(coro, self._loop).result(timeout)

    def __exit__(self, *exc_info: Any) -> None:
        self._loop.call_soon_threadsafe(self._loop.stop)
        self._looper.join()
        self._loop.close()


async def asquare(n: int) -> int:
    print(f"started asquare({n}) [{threading.current_thread().name}]")
    await asyncio.sleep(0.1)
    print(f"finished asquare({n}) [{threading.current_thread().name}]")
    return n * n


def first_even(numbers: Iterable[int]) -> int:
    return next(n for n in numbers if n % 2 == 0)


def main(numbers: Iterable[int]) -> tuple[int, int]:
    coros = map(asquare, numbers)
    with sync_await() as await_:
        x = await_(next(coros))
        y = first_even(map(await_, coros))
    return x, y


async def amain(numbers: Iterable[int]) -> tuple[int, int]:
    coros = map(asquare, numbers)
    with sync_await() as await_:
        x = await next(coros)
        # TypeError: 'async_generator' object is not iterable
        # y = first_even(await c for c in coros)
        y = first_even(map(await_, coros))
    return x, y


if __name__ == "__main__":
    nums = [8, 3, 5, 10, 11, 12, 13]
    print("* main(nums)")
    print(main(nums))
    print()
    print("* asyncio.run(amain(nums))")
    print(asyncio.run(amain(nums)))


# ============= Output ========================
#
# * main(nums)
# started asquare(8) [Thread-1 (run_forever)]
# finished asquare(8) [Thread-1 (run_forever)]
# started asquare(3) [Thread-1 (run_forever)]
# finished asquare(3) [Thread-1 (run_forever)]
# started asquare(5) [Thread-1 (run_forever)]
# finished asquare(5) [Thread-1 (run_forever)]
# started asquare(10) [Thread-1 (run_forever)]
# finished asquare(10) [Thread-1 (run_forever)]
# (64, 100)
# 
# * asyncio.run(amain(nums))
# started asquare(8) [MainThread]
# finished asquare(8) [MainThread]
# started asquare(3) [Thread-2 (run_forever)]
# finished asquare(3) [Thread-2 (run_forever)]
# started asquare(5) [Thread-2 (run_forever)]
# finished asquare(5) [Thread-2 (run_forever)]
# started asquare(10) [Thread-2 (run_forever)]
# finished asquare(10) [Thread-2 (run_forever)]
# (64, 100)