Python购物车代码优化：如何仅用外层while循环实现功能

我是Python及编程领域的新手，正在开发第一个迷你项目——购物车。目前代码可正常运行，但有人告知我可以仅通过外层while循环实现全部逻辑，无需第二层循环。我一整天尝试调整却毫无进展，希望能得到实现思路的指导，谢谢。

原代码 #

shopping_list = []
print("Hi, Welcome to Jolly's Market.")
while True:
    customer = input("To add to the shopping cart, press 1. To checkout and leave press 2.\n")


    if customer == "1":
        print("To return to the menu, type exit . To remove items, type r")
        while customer != "exit" or customer != "r":
            shopping_list.append(input("Add to cart: "))
            print(shopping_list)
            customer = input("").lower()

            if customer == "exit":
                print("Sending you back to the menu")
                break
                

            if customer == "r":
                shopping_list.pop(int(input("Remove item ")))  
                print(shopping_list)
                shopping_list.append(input("Add to cart: "))
                print(shopping_list)
                customer = input("").lower()
            
            if len(shopping_list) == 10:
                print("You have ten items, do you wish to add more? (y, n)")
                customer = input(" ").lower()
            
            if customer == "y":
                shopping_list.append(input("Add to cart: "))
            elif customer == "n":
                print("Sending you back to the main menu")
                break 

单外层循环实现思路 #

核心是用状态变量追踪当前程序所处的阶段（主菜单/添加商品），把原本第二层循环的逻辑拆分到外层循环的不同分支中：

• 定义一个状态变量，比如current_mode，初始值设为"main_menu"，用来标记当前是在主菜单还是添加商品的流程里。
• 外层循环始终运行，每次根据current_mode的值执行对应逻辑：
  1. 主菜单状态：显示1（添加商品）和2（结账离开）的选项。用户选1就把current_mode改成"adding_items"；选2就直接退出循环结束程序。
  2. 添加商品状态：处理添加、删除、返回主菜单的操作：
     • 先提示用户可以输入商品名添加，或输入exit返回菜单、r删除商品。
     • 接收用户输入后分情况处理：
       • 输入exit：打印提示，把current_mode改回"main_menu"，回到主菜单逻辑。
       • 输入r：执行删除操作（注意加简单判断避免索引越界），删除后保持current_mode不变，继续停留在添加流程。
       • 输入商品名：添加到购物车，然后检查购物车长度：
         • 如果长度到10，询问是否继续添加。用户选n就改回主菜单状态；选y就继续允许添加。
     • 所有操作完成后，外层循环会再次执行，根据更新后的current_mode进入对应分支，无需嵌套循环。

调整后的示例代码 #

shopping_list = []
current_mode = "main_menu"  # 状态变量：main_menu 或 adding_items
print("Hi, Welcome to Jolly's Market.")

while True:
    if current_mode == "main_menu":
        customer_choice = input("To add to the shopping cart, press 1. To checkout and leave press 2.\n")
        if customer_choice == "1":
            current_mode = "adding_items"
            print("To return to the menu, type exit. To remove items, type r")
        elif customer_choice == "2":
            print("Checkout complete. Thank you for shopping!")
            break  # 退出外层循环，结束程序
        else:
            print("Invalid input, please enter 1 or 2.")
    
    elif current_mode == "adding_items":
        user_input = input("Add to cart: ").lower()
        
        if user_input == "exit":
            print("Sending you back to the menu")
            current_mode = "main_menu"
        elif user_input == "r":
            if not shopping_list:
                print("Cart is empty, nothing to remove.")
                continue
            try:
                item_index = int(input("Enter the index of the item to remove: "))
                shopping_list.pop(item_index)
                print(f"Updated cart: {shopping_list}")
            except (ValueError, IndexError):
                print("Invalid index, please try again.")
        else:
            # 添加商品到购物车
            shopping_list.append(user_input)
            print(f"Updated cart: {shopping_list}")
            
            # 检查购物车长度是否到10
            if len(shopping_list) == 10:
                more_choice = input("You have ten items, do you wish to add more? (y, n) ").lower()
                if more_choice == "n":
                    print("Sending you back to the main menu")
                    current_mode = "main_menu"
                elif more_choice != "y":
                    print("Invalid input, staying in add mode.")

内容的提问来源于stack exchange，提问作者Lightjolly