Learning Python Through
Rice Retail —
A Complete Walkthrough

from abc import ABC, abstractmethod

class RiceProduct:
    """Represents a single rice product with name and price."""

    def __init__(self, name, price_per_kilo, variety, origin):
        self.name           = name
        self.price_per_kilo = price_per_kilo
        self.variety        = variety
        self.origin         = origin

    def display(self, code):
        print(f"  [{code}] {self.name:<28} ₱{self.price_per_kilo:>6.2f}/kg  ({self.variety}, {self.origin})")


class RiceRetailSystem:
    """Manages the complete rice retail shop experience."""

    def __init__(self):
        self.catalog = {
            "R1": RiceProduct("Sinandomeng Premium",  58.00, "Indica",     "Nueva Ecija"),
            "R2": RiceProduct("Milagrosa Special",     62.00, "Aromatic",   "Batangas"),
            "R3": RiceProduct("Dinorado Heirloom",     75.00, "Heirloom",   "Mountain Province"),
            "R4": RiceProduct("NFA Standard Rice",      40.00, "Indica",     "NFA Warehouse"),
            "R5": RiceProduct("Jasmine Thai Import",    85.00, "Long Grain", "Imported"),
            "R6": RiceProduct("Brown Rice Organic",     95.00, "Whole Grain","Benguet"),
            "R7": RiceProduct("Glutinous Malagkit",    68.00, "Glutinous",  "Pampanga"),
            "R8": RiceProduct("Super Angelica Premium", 70.00, "Indica",     "Isabela"),
        }
        self.cart          = []
        self.customer_name = ""

    def show_banner(self):
        print("\n" + "═" * 60)
        print("       🌾  VALLEYS & BYTES RICE TRADING  🌾")
        print("          Premium Rice Retailer — Philippines")
        print("═" * 60)

    def show_catalog(self):
        print("\n  📦  AVAILABLE RICE PRODUCTS (Price per Kilo):")
        print("  " + "─" * 56)
        for code, product in self.catalog.items():
            product.display(code)
        print("  " + "─" * 56)

    def get_customer_name(self):
        self.customer_name = input("\n  Enter your name: ").strip().title()
        print(f"\n  Welcome, {self.customer_name}! Let's build your order.")

    def add_to_cart(self):
        while True:
            print("\n  Enter product code (or 'DONE' to checkout, 'VIEW' to see cart):")
            code = input("  > ").strip().upper()
            if code == "DONE": break
            elif code == "VIEW": self.show_cart(); continue
            elif code not in self.catalog:
                print("  ❌ Invalid code. Please choose from the menu."); continue
            try:
                kilos = float(input(f"  How many kilos of {self.catalog[code].name}? "))
                if kilos <= 0:
                    print("  ⚠️  Enter a quantity greater than zero."); continue
                self.cart.append((code, kilos))
                print(f"  ✅ Added {kilos}kg — ₱{self.catalog[code].price_per_kilo * kilos:.2f}")
            except ValueError:
                print("  ❌ Please enter a valid numeric quantity.")

    def show_cart(self):
        if not self.cart: print("  🛒 Your cart is empty."); return
        print("\n  Current cart:")
        for i, (code, kilos) in enumerate(self.cart, 1):
            p = self.catalog[code]
            print(f"  {i}. {p.name} × {kilos}kg = ₱{p.price_per_kilo * kilos:.2f}")

    def calculate_total(self):
        return sum(self.catalog[c].price_per_kilo * k for c, k in self.cart)

    def print_receipt(self):
        if not self.cart: print("\n  🛒 No items in cart."); return
        print("\n" + "═" * 60)
        print("          🧾  OFFICIAL RECEIPT  🧾")
        print("          Valleys & Bytes Rice Trading")
        print("═" * 60)
        print(f"  Customer : {self.customer_name}")
        print("  " + "─" * 56)
        print(f"  {'PRODUCT':<30} {'KG':>5}  {'SUBTOTAL':>10}")
        print("  " + "─" * 56)
        for code, kilos in self.cart:
            p = self.catalog[code]; subtotal = p.price_per_kilo * kilos
            print(f"  {p.name:<30} {kilos:>5.1f}  ₱{subtotal:>9.2f}")
        print("  " + "─" * 56)
        print(f"  {'GRAND TOTAL':<36} ₱{self.calculate_total():>9.2f}")
        print("═" * 60)
        print("  Salamat! Thank you for shopping at Valleys & Bytes! 🇵🇭")
        print("═" * 60 + "\n")

    def run(self):
        """Main entry point."""
        self.show_banner(); self.show_catalog()
        self.get_customer_name(); self.add_to_cart()
        self.print_receipt()


if __name__ == "__main__":
    shop = RiceRetailSystem()
    shop.run()