ticker.py

import atexit
import time

from threading import (
    Event,
    Lock,
    Thread,
)


def ticker(interval, function, flush=None):
    """
    Runs the provided function at the given interval.
    """
    cancelled = Event()

    def finish():
        if flush is None:
            return  # nothing to do

        with finish.lock:
            if not finish.executed:
                flush()
                finish.executed = True

    finish.lock = Lock()
    finish.executed = False

    def run():
        while not cancelled.is_set():
            time.sleep(interval)
            function()

        finish()

    t = Thread(None, run)
    t.daemon = True
    t.start()

    if flush:
        atexit.register(finish)

    return cancelled.set


if __name__ == '__main__':
    import itertools
    import sys

    counter = itertools.count(1)
    queue = []

    def ping():
        print 'ping', time.time()
        queue.append(next(counter))

    def flush():
        print queue

    cancel = ticker(1, ping, flush)
    time.sleep(int(sys.argv[1]))
    cancel()