time_mark_example.py

#!/usr/bin/env python3

from datetime import datetime, timedelta
from time import sleep


def time_mark(**timedelta_kwargs):
    mark = datetime.now() + timedelta(**timedelta_kwargs)
    while True:
        yield datetime.now() > mark


if __name__ == '__main__':
    # create generator
    are_we_there_yet = time_mark(seconds=3)

    # annoying kid
    for i in range(5):
        print(next(are_we_there_yet))
        sleep(1)