class ProductCatalog(object):
    @staticmethod
    def lookupDesc(itemID) : pass  # probably some database query
    @staticmethod
    def lookupPrice(itemID) : pass # probably some database query


class Product(object):
    def __init__(self, itemID):
        self.itemID = itemID
        self.description = ProductCatalog.lookupDesc(itemID)
        self.price = ProductCatalog.lookupPrice(itemID)
    def getPrice(self)
        return self.price

class OrderLine(object):
    def __init__(self, productID, quantity):
        self.product = Product(productID)
        self.quantity = quantity
    def getPriceTotal(self):
        return (self.product.getPrice() * self.quantity)

class Sale(object):
    def __init__(self):
        self.LineItems =[]
        self.SaleTotal = 0
    def addLineItem(self,product,quantity):
        ol = Orderline(product,quantity):
        self.LineItems.append((oi.product,oi.quantity,oi.getPriceTotal()))
    def get LineItem(self, num):
        return self.LineItems[num]
    def getSaleTotal(self):
        self.SaleTotal = 0
	for order in self.LineItems:
            self.Total = self.Total + order[2]