class WaiterTimeout(Exception):
    pass


class Waiter(object):
    """
    w = Waiter()
    run_some_func_with_callback(callback=lambda x: w.stop(x))
    try:
        r = w.timeout(5)  # wait 5 seconds for timeout
    except WaiterTimeout:
        print("timeout occured")
    else:
        print("result: {}".format(r))
    """

    def __init__(self, spin=None):
        self.event = threading.Event()
        self.result = None

    def wait(self, timeout=None, spin=0):
        if timeout is None or not spin:
            if self.event.wait(timeout):
                return self.result
            else:
                raise WaiterTimeout

        total = 0
        while total < timeout:
            if self.event.wait(spin):
                return self.result
            total += spin

        raise WaiterTimeout

    def stop(self, result=None):
        self.result = result
        self.event.set()

    def clear(self):
        self.event.clear()
        self.result = None