main.py

import time
from typing import Callable


class ShopCartService:
    def checkout(self) -> None:
        print("Checkout is in progress...")
        time.sleep(3)


class TimedShopCartService(ShopCartService):  # Decorator pattern
    def __init__(self, shop_cart_service: ShopCartService) -> None:
        self._shop_cart_service = shop_cart_service

    @staticmethod
    def _timed_operation(func: Callable) -> None:
        tic = time.perf_counter()

        func()

        toc = time.perf_counter()
        elapsed_time = toc - tic
        print(f"Elapsed time: {elapsed_time:0.4f} seconds")

    def checkout(self) -> None:
        self._timed_operation(lambda: self._shop_cart_service.checkout())


service = TimedShopCartService(ShopCartService())
service.checkout()