A simple periodic callback mechanism that uses the stdlib's threading.Timer

PeriodicTimerCallback

#!/usr/bin/env python3

"""
A periodic callback mechanism that uses `threading.Timer`.
"""


class PeriodicTimerCallback(object):
    """
    A wrapper that uses either `threading.Timer` to call functions at a
    specified interval.  Example::

        >>> from datetime import datetime
        >>> def print_date(): print(datetime.now())
        >>> pc = PeriodicTimerCallback(print_date, 1000)
        >>> pc.start()
        2014-05-10 13:54:58.318233
        2014-05-10 13:54:59.319531
        2014-05-10 13:55:00.320827
        2014-05-10 13:55:01.321875
        >>> pc.stop()
    """
    def __init__(self, callback, callback_time):
        self.callback = callback
        self.callback_time = callback_time
        from threading import Timer
        # NOTE: Timer uses seconds
        def callback_wrapper():
            "Runs the callback and restarts the Timer so it will run again"
            self.callback()
            self._pc = Timer(callback_time / 1000, callback_wrapper)
            if self._running:
                self._pc.start()
        self._pc = Timer(callback_time / 1000, callback_wrapper)
        self._running = False

    def start(self):
        """Starts the timer."""
        self._running = True
        self._pc.start()

    def stop(self):
        """Stops the timer."""
        self._running = False
        self._pc.cancel()