import contextlib import functools import concurrent.futures import threading import sys def fn(num, stop_event): if num == 1: stop_event.wait() return "done 1" if num == 2: return "done 2" def main(): stop_event = threading.Event() log = [] with concurrent.futures.ThreadPoolExecutor(max_workers=1) as pool: def print_n_wait(ident): log.append(f"{ident=} started") try: stop_event.wait() finally: log.append(f"{ident=} stopped") fut = pool.submit(print_n_wait, ident="first") try: with contextlib.closing(pool.map(print_n_wait, ["second", "third"], timeout=1)) as gen: try: next(gen) except concurrent.futures.TimeoutError: print("timed out") else: raise RuntimeError("timeout expected") finally: stop_event.set() assert log == ["ident='first' started", "ident='first' stopped"], f"{log=} is wrong" if __name__ == "__main__": sys.exit(main())