import random
import signal
import threading
import time

class EvilThread(threading.Thread):
    def coroutine(self):
        while True:
            letter = "#" if self.daemon else "."
            print(letter, end="", flush=True)
            try:
                raise ValueError()
            except ValueError as exc:
                delay = random.randint(1, 100) / 1000
                time.sleep(delay)
            else:
                delay = random.randint(1, 100) / 1000
                time.sleep(delay)
            yield

    def run(self):
        gen = self.coroutine()
        for it in gen:
            pass


def main():
    def killer(signum, frame):
        raise KeyboardInterrupt()

    threads = [EvilThread() for index in range(10)]
    #for thread in threads[:len(threads)//2]:
    #    thread.daemon = True
    for thread in threads:
        thread.start()

    signal.signal(signal.SIGALRM, killer)
    signal.alarm(1)

main()