Store Class contains my Main event loop:

from product import Product
from shippingmethod import ShippingMethod
from toolbox import get_string, get_integer, get_positive_number
from address import Address
from customer import Customer
from order import Order
from lineitem import LineItem


class Store(object):

    def __init__(self):
        self.__customers = []
        self.__products = []
        self.read_products('inventory.txt')
        self.__shippingMethods = []
        self.read_shipping_methods('shipping.txt')
        self.__currentCustomer = None
        self.__currentOrder = None

    def __str__(self):
        string = 'products:'
        if self.__products == []:
            string += '\n   none'
        else:
            for product in self.__products:
               string += f'\n   {product}'
        string += '\nshipping methods:'
        if self.__shippingMethods == []:
            string += '\n   none'
        else:
            for method in self.__shippingMethods:
               string += f'\n   {method}'
        string += '\ncustomers:'
        if self.__customers == []:
            string += '\n   none'
        else:
            for customer in self.__customers:
                string += f'\n   {customer.name}'
        return string

    def read_products(self, filename):
        """Read the available products from a file."""
        with open(filename, 'r') as productsFile:
            for line in productsFile:
                name, type, price = line.split(',')
                try:
                    self.__products.append(Product(name, type, price))
                except TypeError:
                    print(f'{name} not added to inventory. Check {filename}.')

    def read_shipping_methods(self, filename):
        """Read the available products from a file."""
        with open(filename, 'r') as shippingFile:
            for line in shippingFile:
                name, description, basePrice, pricePerPound = line.split(',')
                try:
                    self.__shippingMethods.append(ShippingMethod(name, description, basePrice, pricePerPound))
                except TypeError:
                    print(f'{name} not added to shipping methods. Check {filename}.')

    def display_products(self, displayTypes = None):
        """Display all of the products of a certain type or all products (default)."""
        if displayTypes == None:
            displayTypes = Product.types
        else:
            if type(displayTypes) == type('someString'):
                displayTypes = [displayTypes]
        productCounter = 1
        productList = []
        print()
        for displayType in displayTypes:
            for product in self.products:
                if product.type == displayType:
                    print(f'{productCounter}. {product}.')
                    productList.append(product)
                    productCounter += 1
            print()
        return productList

    def display_shipping(self):
        """Display all of the shipping methods."""
        shippingCounter = 1
        shippingList = []
        print()
        for shippingMethod in self.shippingMethods:
            print(f'{shippingCounter}. {shippingMethod}.')
            shippingList.append(shippingMethod)
            shippingCounter += 1
        print()
        return shippingList

    def run(self):
        """Main event loop for the store."""
        command = 'help'
        while command != 'quit':
            if command == 'help':
                self.help()
            elif command == 'add_customer':
                self.add_customer()
            elif command == 'add_order':
                self.add_order()
            elif command == 'add_line_item':
                self.add_line_item()
            elif command == 'try_to_quit':
                self.try_to_quit()
            elif command == 'show_totals':
                self.show_totals()
            if command != 'quit':
                self.show_menu()
                command = self.get_command()

    def add_customer(self):
        """Add the next customer."""
        #TODO add new customer to the customers list right after creation.
        #TODO Move this to Customer Class.
        if self.__currentCustomer != None:
            if self.__currentOrder != None:
                self.__currentCustomer.add(self.__currentOrder)
                self.__currentOrder = None
            self.__customers.append(self.__currentCustomer)
        name = get_string("What is the customer's name?")
        #TODO Move this to Address Class.
        street = get_string("street address?")
        city = get_string("city?")
        state = get_string("state?")
        zipcode = get_string("zipcode?")
        try:
            address = Address(street, city, state, zipcode)
            customer = Customer(name, address)
            self.__currentCustomer = customer
        except:
            print('Could not create a customer with that address.')

    def add_order(self):
        """Create an order. It is not yet added to the customer."""
        if (self.__currentOrder != None) and (len(self.__currentOrder) > 0):
            self.__currentCustomer.add(self.__currentOrder)
        #
        # Get shipping method.
        #
        #TODO Move this to ShippingMethod Class.
        shippingMethods = self.display_shipping()
        validShippingMethods = range(1,len(shippingMethods)+1)
        userInput = 'x'
        while userInput not in validShippingMethods:
            userInput = get_integer('Which shipping method?')
        shippingMethod = shippingMethods[userInput - 1]
        #
        # Get Address
        #
        #TODO Let the user pick a differnt address
        address = self.__currentCustomer.address
        self.__currentOrder = Order(shippingMethod, address)

    def add_line_item(self):
        """Create a new line item and add it to the current order."""
        if self.__currentOrder == None:
            self.add_order()
        products = self.display_products()
        validProducts = range(1,len(products)+1)
        userInput = 'x'
        while userInput not in validProducts:
            userInput = get_integer('Which product?')
        product = products[userInput - 1]
        amount = get_positive_number('How much?')
        self.__currentOrder.add(product, amount)

    def show_totals(self):
        print()
        print(f"Total Sales:    ${self.sales():10.2f}")
        print(f"Total Shipping: ${self.shipping():10.2f}")
        print(f"Total Tax:      ${self.tax():10.2f}")

    def show_menu(self):
        print('[S]how totals   [H]elp   [Q]uit   Add: [C]ustomer [O]rder [L]ineItem    ')

    def get_command(self):
        """Ask for and validate user commands."""

        commands = {'s': 'show_totals',
                    'h': 'help',
                    '?': 'help',
                    'q': 'try_to_quit',
                    'c': 'add_customer',
                    'o': 'add_order',
                    'l': 'add_line_item'}

        validInputs = commands.keys()

        userInput = 'xxx'
        while userInput not in validInputs:
            userInput = input('Command:')[0].lower()
        return commands[userInput]

    def help(self):
        print()
        print("I haven't had a chance to write instructions.")
        print()

    def sales(self):
        """Returns the total dollar amount sold today."""
        sales = 0
        for customer in self.customers:
            for order in customer.orders:
                sales += order.sales
        return sales

    def shipping(self):
        """Returns the total shipping amount today."""
        shipping = 0
        for customer in self.customers:
            for order in customer.orders:
                shipping += order.shippingCost
        return shipping

    def tax(self):
        """Returns the total tax collected today."""
        tax = 0
        for customer in self.customers:
            for order in customer.orders:
                tax += order.tax
        return tax

    def get_products(self):
        return self.__products

    def get_shipping_methods(self):
        return self.__shippingMethods

    def get_customers(self):
        return self.__customers

    products = property(get_products)
    shippingMethods = property(get_shipping_methods)
    customers = property(get_customers)

Anything else?