A simple timer for me that counts from zero upward!

timer.py

#!/usr/bin/env python3

"""\
. . .
timer
. . .

A timer that counts from time 0 to the final time

USAGE: timer <secs>
"""

from sys import argv
from time import sleep


def main() -> int:
    """Main function"""
    
    # Get end time from command-line
    try:
        end_time: int = int(argv[1])
    except ValueError:
        print("Usage: timer <secs>")
        return 1

    print(f"Set timer for {end_time} seconds")

    sec: int = 0
    minute: int = 0
    hour: int = 0

    for _ in range(1, end_time + 1):
        sec += 1
        if minute == 60:
            hour += 1
            minute = 0
        if sec == 60:
            minute += 1
            sec = 0
        print(f"Time: {hour:02d}:{minute:02d}:{sec:02d}", end="\r")
        sleep(1)

    print(f"Time: {hour:02d}:{minute:02d}:{sec:02d}")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())