threading workers printer not complete

from argparse import ArgumentParser
import time
from random import random
from threading import Thread, Event
from queue import Queue, Empty


class MyThread(Thread):

    def __init__(self, thread_id, name, counter, message, result_queue, event):
        super().__init__()
        self.thread_id = thread_id
        self.name = name
        self.counter = counter
        self.message = message
        self.result_queue = result_queue
        self.event = event

    def run(self):
        print (f"{self.name} started")
        for i in range(self.counter):
            # each iteration simulates a big_calculation
            # looking, if self.event is set
            if self.event.is_set():
                break
                # thread ends here
                # if event is_set
            time.sleep(random() * 5)
            # simulates random time for computation
            self.result_queue.put(self.message)
        # for-loop is finite


class Printer(Thread):
    def __init__(self, result_queue, event):
        super().__init__()
        self.result_queue = result_queue
        self.event = event
    def run(self):
        while not self.event.is_set():
            try:
                result = self.result_queue.get_nowait()
            except Empty:
                time.sleep(0.5)
            else:
                self.result_queue.task_done()
                print(result)


def main(workers):
    result_queue = Queue()
    event = Event()
    threads = [
        MyThread(
            thread_id=n,
            name=f'Thread {n}',
            counter=15,
            message=f'Do something {n}',
            result_queue=result_queue,
            event=event,
        )
        for n in range(1, workers + 1)
    ]
    [t.start() for t in threads]
    print("Threads started, adding printer")
    printer = Printer(result_queue, event)
    printer.start()
    print("Sleeping for 10 seconds")
    time.sleep(10)
    print("Set event, which will end all threads after the next iteration of all threads")
    event.set()


if __name__ == '__main__':
    parser = ArgumentParser(description='Example program for threads')
    parser.add_argument('threads', type=int, help='Amount of worker threads')
    args = parser.parse_args()
    main(args.threads)