### 创建一个不依赖外部模块的简单Python订餐系统 为了创建一个仅使用标准库编写的简单网上订餐系统，可以遵循基本的对象导向原则来定义几个核心类：`User`, `Menu`, 和 `Order`. 这种方法能够确保程序结构清晰，并且易于扩展。 #### 定义用户类 首先，定义一个表示用户的类。这个类负责处理用户的身份验证和个人信息管理： ```python class User: def __init__(self, username, password): self.username = username self.password = password def authenticate(self, input_password): return self.password == input_password ``` #### 构建菜单类 接着，构建一个代表餐厅菜单的类。该类允许添加新菜品到菜单中，并能显示所有可用选项给顾客查看： ```python class Menu: def __init__(self): self.items = {} def add_item(self, name, price): self.items[name] = float(price) def show_menu(self): print("Menu:") for item_name, item_price in self.items.items(): print(f"{item_name}: ${item_price:.2f}") ``` #### 实现订单类 最后，建立一个用于记录客户所下订单详情的类。此部分还包括计算总金额的方法： ```python class Order: def __init__(self): self.order_items = [] def place_order(self, menu, *items): total_cost = 0.0 for item in items: if item not in menu.items: raise ValueError(f"Item '{item}' is not available on the menu.") cost = menu.items[item] self.order_items.append((item, cost)) total_cost += cost print(f"\nYour order has been placed successfully!") print("Items ordered and their costs are as follows:\n") for i, (name, cost) in enumerate(self.order_items, start=1): print(f"{i}. {name} - ${cost:.2f}") print(f"\nThe total amount due is: ${total_cost:.2f}\n") if __name__ == "__main__": # 初始化数据 user = User('admin', 'password') authenticated = False while not authenticated: pwd_input = input("Enter your password to log in: ") authenticated = user.authenticate(pwd_input) if not authenticated: print("Incorrect Password! Try again.\n") my_menu = Menu() my_menu.add_item("Pizza", "9.99") my_menu.add_item("Pasta", "7.50") my_menu.show_menu() customer_order = Order() try: selected_items = ["Pizza"] customer_order.place_order(my_menu, *selected_items) except Exception as e: print(e) ``` 上述代码展示了如何通过纯 Python 编写一个简易版的在线订餐应用程序[^1]。尽管这里展示的例子非常基础，但它已经涵盖了登录认证、浏览菜单以及下单这几个关键环节。当然，在实际应用环境中还需要考虑更多细节问题，比如安全性增强措施、异常情况下的恢复策略等。