Convert 24-hour time to formatted 12-hour time

24_to_12.py

#!/usr/local/bin/python3

import sys
import re

input_text = sys.stdin.read()
regex_24 = re.compile(r'''\b
                          ([01][0-9]|2[0-3]) # Hour (00-23)
                          ([0-5][0-9])       # Mins (00-59)
                          \b''', flags=re.VERBOSE)

def convert_24(match):
    hour, minute = match.groups()
    hour = int(hour)

    if hour < 12:
        suffix = 'am'
    else:
        suffix = 'pm'

    if hour == 0:
        hour = '12'
    elif hour > 12:
        hour -= 12

    if minute == '00':
        return '{h}{sf}'.format(h=hour, sf=suffix)
    else:
        return '{h}.{m}{sf}'.format(h=hour, m=minute, sf=suffix)

working = regex_24.sub(convert_24, input_text)
print(working)

24_to_12_v2.py

#!/usr/local/bin/python3
 
import sys
import re
from datetime import time
 
input_text = sys.stdin.read()
regex_24 = re.compile(r'''\b
                          ([01][0-9]|2[0-3]) # Hour (00-23)
                          :?
                          ([0-5][0-9])       # Mins (00-59)
                          \b''', flags=re.VERBOSE)
 
def convert_24(match):
    hour, minute = [int(part) for part in match.groups()]
    tm = time(hour, minute)
    fmt = '%-I.%M%p' if minute else '%-I%p'
    return tm.strftime(fmt).lower()
 
working = regex_24.sub(convert_24, input_text)
print(working)