Program calculates time such as 5:5 + 22:16 + 1:23:45 in hh:mm:ss format. It allows to enter time with '.' or with ':' as a time separator

time_calc.py

import sys
import datetime
from time import strptime


def process_input(user_input):
    """Parses user input and returns parsed time. """
    time_separator = '.'
    time_tokens = 3

    user_input = user_input.replace(':', time_separator)     # replace separator to common one

    tokens = len(user_input.split(time_separator))
    if tokens > time_tokens:
        raise ValueError('Invalid time format. It has to be in hh.mm.ss, mm.ss or ss format')

    partitions = time_separator.join('%H.%M.%S'.split(time_separator)[-tokens:])

    return strptime(user_input, partitions)


def collect_data():
    """Collects time. """
    total_time = datetime.datetime(1,1,1)
    print('Enter time in format following format hh.mm.ss, mm.ss or ss. Press Enter key to exit')
    while True:
        try:
            user_input = input()
            if user_input == '':
                print('\nTotal time:', total_time.time())
                break
            else:
                entered_time = process_input(user_input)
                total_time += datetime.timedelta(hours=entered_time.tm_hour, minutes=entered_time.tm_min, seconds=entered_time.tm_sec)
                print(total_time.time())
        except ValueError as e:
            print (str(e))


def main():
    """Main function and starting point of the program. """
    try:
        collect_data()
        sys.exit(0)
    except Exception as e:
        print('Unhandled exception', str(e))
        sys.exit(1)


main()