step date range, generate slot list

gistfile1.py

def step_date_range(start, end, **step):
    """
    Returns a range
    :param start: datetime
    :param end: datetime
    :param step: keywords used in timedelta
    :return: generator of date ranges

    >>> list(step_date_range(datetime(2014, 12, 22, 0, 0),
    ...                      datetime(2014, 12, 22, 2, 50),
    ...                      minutes=30))
    [datetime.datetime(2014, 12, 22, 0, 0), datetime.datetime(2014, 12, 22, 0, 30), \
datetime.datetime(2014, 12, 22, 1, 0), datetime.datetime(2014, 12, 22, 1, 30), \
datetime.datetime(2014, 12, 22, 2, 0), datetime.datetime(2014, 12, 22, 2, 30)]
    """
    current = start
    while current <= end:
        yield current
        current = current + timedelta(**step)


def generate_slot_list(start, end, step):
    """
    Return a list of slots base on start time, end time and step.
    :param start: tuple with (hour, minute) that list should start
    :param end: tuple with (hour, minute) that list should stop
    :param step: int from 1 to 59 indicating how minutes will be used as step
    :return: list of slots like ['00:00 - 00:30', '00:30 - 01:00', '01:00 - 01:30', ...]

    >>> list(generate_slot_list((0, 0), (2, 45), 30))
    ['00:00 - 00:30', '00:30 - 01:00', '01:00 - 01:30', '01:30 - 02:00', '02:00 - 02:30']
    """
    assert 0 < step < 60, "step need to be between 1 and 59."

    today = datetime.today()
    date_range = step_date_range(today.replace(hour=start[0], minute=start[1]),
                                 today.replace(hour=end[0], minute=end[1]),
                                 minutes=step)
    date_start = date_range.next()
    for date_end in date_range:
        yield '{:02d}:{:02d} - {:02d}:{:02d}'.format(date_start.hour, date_start.minute,
                                                     date_end.hour, date_end.minute)
        date_start = date_end