Calculate and sum time differences easily

time_calc.py

# Copyright © 2020 HacKan
# This work is free. You can redistribute it and/or modify it under the
# terms of the Do What The Fuck You Want To Public License, Version 2,
# as published by Sam Hocevar. See http://www.wtfpl.net/ for more details.
#
# This software is provided as-is. You are free to use, share, modify
# and share modifications under the terms of that license. Attribution
# is not required to share but is appreciated.
"""Calculate and sum time differences easily.

Requires Python 3.5+
"""

import re
from datetime import timedelta
from math import ceil
from typing import Optional


def timedelta_from_string(string: str) -> Optional[timedelta]:
    """Convert a string matching a time pattern to a timedelta if possible."""
    time_pattern = re.compile(r'^(\d{1,2})[\D]?(\d{2})$')  # type: re.Pattern
    time_match = time_pattern.match(string)  # type: Optional[re.Match[str]]
    if not time_match:
        return None

    hours, minutes = map(int, time_match.groups())  # type: int
    time_part = timedelta(hours=hours, minutes=minutes)  # type: timedelta
    return time_part



print(
    'Time difference sum calculator.',
    'For time ranges: input time ranges one part at a time: every two ',
    'consecutive inputs is considered a range. Then leave empty to calculate.',
    'The minute value is rounded up when displaying results.',
    'The input format is roughly HH:MM or H:MM (actually the separator may be ',
    'anything or nothing, not just ":").',
    sep='\n',
)

total_seconds = 0  # type: int
prev_time_part = None  # type: Optional[timedelta]

print('Time ranges')
while True:
    raw_time = input(
        'Input time (leave empty to continue): ',
    )
    if not raw_time:
        if not prev_time_part:
            break  # Exit

        print('Missing time range part')
        continue

    time_part = timedelta_from_string(raw_time)  # type: Optional[timedelta]
    if not time_part:
        print('Wrong input format')
        continue

    if prev_time_part:
        if time_part > prev_time_part:
            difference = time_part - prev_time_part
        else:
            difference = prev_time_part - time_part
        total_seconds += difference.total_seconds()
        prev_time_part = None
    else:
        prev_time_part = time_part

print()
print('Time lapses')
while True:
    raw_time = input(
        'Input time (leave empty to continue): ',
    )
    if not raw_time:
        break  # Exit

    time_part = timedelta_from_string(raw_time)  # type: Optional[timedelta]
    if not time_part:
        print('Wrong input format')
        continue

    total_seconds += time_part.total_seconds()

print()
print(
    'Total time:',
    int(total_seconds // 3600),
    'h',
    ceil((total_seconds % 3600) / 60),
    'm',
)