Some algorithm thing

algorithm1.py

import sys

HELP = """
python3 algorithm1.py -h
  show this very help page
python3 algorithm1.py
  work out what's special about 495
python3 algorithm1.py <number>
  run the algorithm on <number>
"""

def smallest(digits: list) -> int:
    digits.sort()
    return int(''.join(digits))

def largest(digits: list) -> int:
    digits.sort()
    return int(''.join(reversed(digits)))

def once(digits: list, exit=lambda: None, print=lambda *a, **k: None) -> list:
    s = smallest(digits)
    l = largest(digits)
    r = l - s
    print(f"{l} - {s} = {r}")
    if r == 0: print("\033[1mGot to zero, exiting\033[0m"); exit()
    return list(str(r))

def whats_special_about_495() -> None:
    for num in range(1000):
        ln = list(str(num))
        if set(n := once(ln)) == set(ln):
            print("\033[1mOther number like 495:", int(''.join(n)), end='\033[0m\n')

if __name__ == '__main__':
    if len(sys.argv) == 1: whats_special_about_495()
    if sys.argv[-1] in {'-h', '--help'}: print(HELP)
    digits = list(sys.argv[-1][:3])
    while 1:
        digits = once(digits, sys.exit, print)
        print(f"Next digits {digits!r}")
        if digits == list('495'):
            print("\033[1mWE GOT TO 495\033[0m"); exit()

Provide number to process as command-line argument. TODO: if no arguments are passed, process all 3-digit numbers.