Python咖啡店程序运行异常求助：总金额计算结果错误

核心问题诊断 #

1. 金额计算错误：input()获取的quantity是字符串类型，字符串与数字相乘会执行字符串重复操作（例如"4" * 120会生成120个"4"拼接的字符串），而非数值乘法，导致总金额输出大量重复数字。
2. 未定义变量错误：代码中多次调用coffee[0]、coffee[1]等，但从未定义过coffee变量，实际运行时会触发NameError（当前运行结果未显示是因为程序在报错前已完成了金额打印）。

修复后的完整代码 #

prices = [120, 130, 120, 150]

menu = {
    1: ["Latte", 120],
    2: ["Capputino", 130],
    3: ["Americano", 120],
    4: ["Espresso", 150]
}

headers = ["No.", 'Name', "Price"]
print(f'{headers[0]: <10}{headers[1]: <15}{headers[2]}')

for value, key in menu.items():
    print(f'{value: <10}{key[0]: <15}{key[1]}')

myorder_coffee = []
myorder_cost = []
total = 0

print("Welcome to COFFEE & DELIGHT")

name = input("Enter your name: ")
order = input("Enter the name of your order: ")
# 将输入的数量转换为整数，确保数值计算有效
quantity = int(input("Enter the amount of drinks you want to order: "))

if order == "Latte":
    myorder_coffee.append(order)
    myorder_cost.append(prices[0])
    total = quantity * 120
    print(name, "ordered", quantity, "Latte")
    print("Total amount to be paid=", total)
elif order == "Capputino":
    myorder_coffee.append(order)
    myorder_cost.append(prices[1])
    total = quantity * 130
    print(name, "ordered", quantity, "Capputino")
    print("Total amount to be paid=", total)
elif order == "Americano":
    myorder_coffee.append(order)
    myorder_cost.append(prices[2])
    total = quantity * 120
    print(name, "ordered", quantity, "Americano")
    print("Total amount to be paid=", total)
elif order == "Espresso":
    myorder_coffee.append(order)
    myorder_cost.append(prices[3])
    total = quantity * 150
    print(name, "ordered", quantity, "Espresso")
    print("Total amount to be paid=", total)
else:
    print("Item not in menu")

关键修复说明 #

• 类型转换：将quantity的输入值通过int()转为整数类型，保证后续乘法是数值运算而非字符串重复。
• 变量替换：删除对未定义coffee变量的引用，直接使用用户输入的order字符串添加到订单列表中，逻辑更直接。

可选优化（简化代码） #

原有的if-elif链冗余度高，可利用menu字典遍历匹配订单，新增品类时无需修改多个分支：

# 替换原有的if-elif代码块
order_found = False
for coffee_info in menu.values():
    coffee_name, coffee_price = coffee_info
    if coffee_name == order:
        myorder_coffee.append(coffee_name)
        myorder_cost.append(coffee_price)
        total = quantity * coffee_price
        print(f"{name} ordered {quantity} {coffee_name}")
        print(f"Total amount to be paid= {total}")
        order_found = True
        break
if not order_found:
    print("Item not in menu")

内容的提问来源于stack exchange，提问作者Fish pp