Take in a GitHub-Flavored-Markdown time tracking list and output total times

calculate_timesheet.py

import sys
import re
from collections import defaultdict

# Script takes in a GitHub-Flavored-Markdown table assuming the following format:
#
# Start | Stop | Task
# ----- | ---- | ----
# 9:20 | 9:40 | Email/Admin
# 9:40 | 11:30 | Automation
# 11:30 | 12:00 | Meeting
# 12:15 | 2:30 | Automation
# 2:30 | 3:00 | Meeting
# 3:00 | 3:30 | Automation
# 3:30 | 4:00 | Meeting
# 4:00 | 5:45 | Automation
# 5:45 | 6:00 | Admin

# Script then outputs the same table, and appends the following table:
#
# Task | Total Time
# ---- | ----------
# Admin | 0.25
# Automation | 6.33
# Meeting | 1.5
# Email/Admin | 0.34
# Total | 8.42

table_lines = []

for i in sys.argv[1:]: 
    table_lines.append(i)

## The line after this comment is a workaround for a macOS Automator issue where input is not given as separate arguments, 
##     but as newline-separated text
# table_lines = table_lines[0].splitlines() 

def decimal_time(input_time):
    time_hour, time_minute = input_time.split(":")
    minute_int = round(float(time_minute) * 1.666666)
    minute_decimal = minute_int / 100
    return float(time_hour) + minute_decimal

def calculate_time(start_time, end_time):
    if end_time < start_time:
        end_time = end_time + 12
    return end_time - start_time

error = False
output_lines = []

for line in table_lines:
    if re.match(r'^[0-9]', line):
        validation_regex = r'(^[0-9]{1,2}:[0-9]{2}) \| ([0-9]{1,2}:[0-9]{2}) \| (.+)'
        if not re.match(validation_regex, line):
            error = True
            break
        start, end, category = re.search(validation_regex, line).groups()
        hours_spent = calculate_time(decimal_time(start), decimal_time(end))
        output_lines.append((category, hours_spent))
        
merged_times = defaultdict(float)

for k, v in output_lines:
    merged_times[k] += v

if error:
    print("\n".join(table_lines))
else:
    total_time = 0
    print("\n".join(table_lines))
    print
    print("Task | Total Time")
    print("---- | ----------")
    for k, v in merged_times.iteritems():
        print(" | ".join((str(k), str(v))))
        total_time += v
    print("Total | " + str(total_time))