import datetime

def to_timedelta (time):
    """
    Transform a datetime or a time instance to a timedelta,
    only using time info
    """
    return datetime.timedelta(
        hours = time.hour,
        minutes = time.minute,
        seconds = time.second
    )

def seconds_to_time (seconds):
    """
    Seconds to datetime.time
    """
    minutes, seconds = divmod(seconds, 60)
    hours, minutes = divmod(minutes, 60)
    return datetime.time(hour = hours, minute = minutes, second = seconds)

def time_sum (times):
    """
    Sum up a list of time elements
    """
    seconds = sum([ time.hour * 3600 + time.minute * 60 + time.second
                    for time in times ])
    return seconds_to_time(seconds)