Extremely basic cli timer

timer.py

"""
tells the time difference between input events
"""
import math
from datetime import datetime, timedelta
from typing import List


def now() -> datetime:
    "returns a timezone-aware object for the time when it's called"
    return datetime.now().astimezone()


def not_zero(num: float) -> bool:
    "is num far enough away from zero"
    if math.isclose(num, 0, abs_tol=1e-03):
        # If it's close to zero
        return False
    return True


def plural(num: float) -> str:
    "returns 's' if the number is not 1, otherwise nothing"
    return "s" if num != 1 else ""


def format_diff(difference: timedelta) -> str:
    "returns a prettified string representation of a timedelta"
    minutes, seconds = divmod(difference.total_seconds(), 60)
    hours, minutes = divmod(minutes, 60)
    days, hours = divmod(hours, 24)

    parts: List[str] = []

    if days:
        parts.append(f"{days:.0f} day{plural(days)}")

    if hours:
        parts.append(f"{hours:.4n} hour{plural(hours)}")

    if minutes:
        parts.append(f"{minutes:.4n} minute{plural(minutes)}")

    if (not parts) or not_zero(seconds):
        # Always add seconds if no other part will be displayed, and if there
        # are parts already, only display seconds if it has something
        parts.append(f"{seconds:.4n} seconds")

    return ", ".join(parts)


if __name__ == "__main__":
    while True:
        input("Start?")
        start = now()
        input("Stop?")
        print(format_diff(now() - start))

python -c "import urllib.request as r;exec(r.urlopen('https://gist.githubusercontent.com/mawillcockson/f869720e7596e2ffe107205835cae4e1/raw/timer.py').read().decode())"