Source Code
Explained —
Book Store Edition

from datetime import datetime
from typing import Dict, Optional

class Book:
    """Represents a single book in the bookstore inventory."""

    def __init__(self, title: str, author: str, price_php: float, quantity: int):
        self.title     = title.strip()
        self.author    = author.strip()
        self.price_php = round(float(price_php), 2)
        self.quantity  = max(0, int(quantity))

    def __str__(self) -> str:
        return f"{self.title:<45} | {self.author:<30} | ₱{self.price_php:>8,.2f} | Stock: {self.quantity:>2}"

    def can_sell(self, qty: int) -> bool:
        return 0 < qty <= self.quantity

    def sell(self, qty: int):
        self.quantity -= qty

class Bookstore:
    """Manages the bookstore inventory and sales."""

    def __init__(self, name: str = "Narra Book Haven"):
        self.name      = name
        self.books: Dict[str, Book] = {}
        self.sales_log: list = []

    def add_book(self, title: str, author: str, price_php: float, quantity: int = 15) -> None:
        key = title.strip().lower()
        if key in self.books:
            self.books[key].quantity += max(0, quantity)
        else:
            self.books[key] = Book(title, author, price_php, quantity)

    def find_book(self, search_term: str) -> Optional[Book]:
        """Supports searching by Title or Row Number."""
        search_term = search_term.strip().lower()
        if search_term.isdigit():
            idx = int(search_term) - 1
            all_books = list(self.books.values())
            if 0 <= idx < len(all_books):
                return all_books[idx]
        return self.books.get(search_term)

    def purchase(self, customer_name: str, title_or_idx: str, quantity: int) -> None:
        book = self.find_book(title_or_idx)
        if not book:
            print(f"\n  [!] '{title_or_idx}' not found.")
            return
        if quantity < 1:
            print("\n  [!] Quantity must be at least 1.")
            return
        if not book.can_sell(quantity):
            print(f"\n  [!] Only {book.quantity} copies left.")
            return
        total     = book.price_php * quantity
        book.sell(quantity)
        timestamp = datetime.now().strftime("%Y-%m-%d %I:%M %p")
        self.sales_log.append({
            "time": timestamp, "customer": customer_name,
            "title": book.title, "qty": quantity, "total": total
        })
        print(f"\n  ✅ Purchase successful!")
        print(f"  Customer: {customer_name} | Total: ₱{total:,.2f}")

def main():
    store = Bookstore("Narra Book Haven")
    store.populate_with_sample_books()
    print("="*90)
    print(f"{store.name:^90}")
    print("="*90)
    while True:
        print("\n[1] View All Books  [2] Buy a Book  [3] Exit")
        choice = input("Enter Choice: ").strip()
        if choice == "1":
            store.list_available_books()
        elif choice == "2":
            store.list_available_books()
            target = input("Enter Title or Number (#): ").strip()
            try:
                qty = int(input("How many copies? : "))
            except ValueError:
                print("  Invalid quantity."); continue
            customer = input("Your name: ").strip() or "Guest"
            store.purchase(customer, target, qty)
        elif choice == "3":
            total_rev = sum(s['total'] for s in store.sales_log)
            print(f"\nTotal Revenue: ₱{total_rev:,.2f}")
            print(f"Thank you for visiting {store.name}!")
            break

if __name__ == "__main__":
    main()