"""A timer class. Should probably be part of threading.py"""

import threading


class Timer(threading.Thread):
    """Call a function after a specified number of seconds:
    
    t = Timer(30.0, f, args=[], kwargs={})
    t.start()
    t.cancel() # stop the timer's action if it's still waiting
    """
    
    def __init__(self, interval, function, args=[], kwargs={}):
        threading.Thread.__init__(self)
        self.interval = interval
        self.function = function
        self.args = args
        self.kwargs = kwargs
        self.finished = threading.Event()
    
    def cancel(self):
        """Stop the timer if it hasn't finished yet"""
        self.finished.set()
    
    def run(self):
        self.finished.wait(self.interval)
        if not self.finished.isSet():
            self.function(*self.args, **self.kwargs)
        self.finished.set()