Python 3.x点餐程序for循环未累加全部总价，仅计算最后一项商品总价的问题求助

Hey there! I see the issue with your order total—let’s break it down and fix it step by step.

What’s Going Wrong #

1. Resetting Totals Every Time: In your loop, every time you select one item, you’re setting all the other totalX variables to 0. For example, if you first order Macaroni Pizza (total1=30), then Garlic Bread, the else clause for order=="1" will set total1 back to 0. By the end of the loop, only the last item’s total has a value, others are 0.
2. Not Accumulating a Running Total: You’re trying to combine the totalX variables into a tuple at the end (total_price = total1, total2...) instead of adding them up. Even if the variables weren’t reset, this would just show a list of numbers, not the sum.
3. Overwriting Variables in the Loop: Each iteration of the loop reuses the same totalX variables, so previous order data gets lost.

Here’s the Fixed Code #

Let’s simplify things with a dictionary to store menu items (makes the code cleaner) and use a single running total:

import sys

print("Welcome to Terry's Restaurant!")

# Store menu items in a dictionary for easier access
menu = {
    "1": {"name": "Macaroni Pizza", "price": 15},
    "2": {"name": "Garlic Bread", "price": 6},
    "3": {"name": "Coca Cola", "price": 4},
    "4": {"name": "Onion Rings", "price": 4},
    "5": {"name": "Fries", "price": 4},
    "0": {"name": "Cancel Order", "price": 0}
}

print("""Please choose items from : 
1. Macaroni Pizza 
2. Garlic Bread 
3. Coca Cola 
4. Onion Rings 
5. Fries 
0. To exit shop/cancel order""")

# Initialize running total
total_price = 0

num_items = int(input("Please enter 1-4 items to be ordered, type 0 to cancel order: "))
if num_items == 0:
    print("Cancelling Order. Thank you come again")
    sys.exit()

for _ in range(num_items):
    while True:
        order = input("\nPlease enter your desired item using 1-5 (0 to cancel): ")
        if order in menu:
            break
        print("Please enter a valid item (1-5 or 0 to cancel)")
    
    if order == "0":
        print("Cancelling Order. Thank you come again")
        sys.exit()
    
    item = menu[order]
    quantity = int(input(f"How many would you like of {item['name']}? "))
    item_total = quantity * item["price"]
    print(f"{quantity} {item['name']} ${item_total}")
    # Add this item's total to the running total
    total_price += item_total

print(f"\nYour order total is ${total_price}")

Key Improvements #

• Running Total: We start with total_price = 0 and add each item’s total to it every time an order is placed—no more losing previous values.
• Menu Dictionary: This replaces all the repetitive if-else blocks, making the code easier to read and update (you can add new menu items just by updating the dictionary).
• Input Validation: The while True loop ensures the user enters a valid menu option before proceeding, so no more invalid input messages popping up incorrectly.
• Cleaner Variable Usage: No more separate total1, total2 variables—we calculate each item’s total on the fly and add it to the main total.

Why Your Original Code Failed #

Let’s recap with an example: if you ordered 2 Macaroni Pizza (total1=30) then 1 Garlic Bread:

• First loop: total1=30, total2-5=0
• Second loop: the else for order=="1" sets total1=0, then total2=6
• At the end, total_price = (0,6,0,0,0)—which is why you only saw the last item’s value.

With the fixed code, each item’s total gets added to total_price immediately, so you end up with 30+6=36 as the final total.

内容的提问来源于stack exchange，提问作者WRonin