python - 带有预告片值的嵌套 while 循环

Question

我的程序的目的是成为一名虚拟的麦当劳收银员。我的程序的第一部分让收银员接受一个顾客的订单。多亏了 while 循环，客户可以订购任意数量的商品。最后它会显示税费、小计和最终账单。以及用户支付的金额及其找零。现在我需要我的程序来完成第一部分的所有操作，但我需要用户/收银员为尽可能多的排队顾客执行此操作。我尝试将两个 while 循环嵌套在一起，但我做错了一些事情，而且我不知道是什么。有人能帮我吗？顺便说一句，第一部分 100% 有效。

第一部分

num1 = 4.87
num2 = 5.03
num3 = 5.50
num4 = 9.45
num5 = 1.29
num6 = 2.19
num7 = 2.29
itemnum = 0
Subtotal = 0
tax = 0.0565
amtgiven = 0
change = 0
quantity = 0
foodprice = 0
Totalprice1 = 0
Totalprice2 = 0
Totalprice3 = 0
Totalprice4 = 0
Totalprice5 = 0
Totalprice6 = 0
Totalprice7 = 0
billtax = 0
finalbill = 0
change = 0

print "Welcome to Virtual McDonald's!"   "Would you like to order a food item"
print "Item:                     Meal/tem:                          Price:"
print "1                          Big Mac Meal                        4.87"
print "2                          Quarter Pounder Meal                5.03"
print "3                          Chicken Nuggets Meal (5 piece)      5.50"
print "4                          ChickenNuggets Meal (10 piece)      9.45"
print "5                          Apple Pie                           1.29"
print "6                          Large Drink                         2.19"
print "7                          Large Fries                         2.29"

itemnum = input("Enter the item you would like to purchase! ")
quantity = input("How many of this item do you want?")
while itemnum != -1:

    if itemnum == 1:
        foodprice = quantity * num1
        Totalprice1 = foodprice

    if itemnum == 2:
        foodprice = quantity * num2
        Totalprice2 = foodprice

    if itemnum == 3:
        foodprice = quantity * num3
        Totalprice3 = foodprice

    if itemnum == 4:
        foodprice == quantity * num4
        Totalprice4 = foodprice

    if itemnum == 5:
        foodprice = quantity * num5
        Totalprice5 = foodprice

    if itemnum == 6:
        foodprice == quantity * num6
        Totalprice6 = foodprice

    if itemnum == 7:
        foodprice = quantity * num7
        Totalprice7 = foodprice   

    subtotal = Totalprice1 + Totalprice2 + Totalprice3 + Totalprice4 + Totalprice5 + Totalprice6 + Totalprice7 
    billtax = subtotal * tax
    finalbill = subtotal + billtax
    itemnum = input("Enter the item you would like to purchase! ")
    quantity = input("How many of this item do you want?")

print "Your total bill without tax is... ", round(subtotal,2)
print "Your total tax is... ", round(billtax,2)
print "Your final bill is... ", round(finalbill,2)
amtgiven = input ("How much do you want to pay with?")
change = amtgiven - finalbill
print "Your change is... ", round(change,2)

第二部分

num1 = 4.87
num2 = 5.03
num3 = 5.50
num4 = 9.45
num5 = 1.29
num6 = 2.19
num7 = 2.29
itemnum = 0
Subtotal = 0
tax = 0.0565
amtgiven = 0
change = 0
quantity = 0
foodprice = 0
Totalprice1 = 0
Totalprice2 = 0
Totalprice3 = 0
Totalprice4 = 0
Totalprice5 = 0
Totalprice6 = 0
Totalprice7 = 0
billtax = 0
finalbill = 0
change = 0
customer = 0

print "Welcome to Virtual McDonald's!"   "Would you like to order a food item"
print "Item:                     Meal/tem:                          Price:"
print "1                          Big Mac Meal                        4.87"
print "2                          Quarter Pounder Meal                5.03"
print "3                          Chicken Nuggets Meal (5 piece)      5.50"
print "4                          ChickenNuggets Meal (10 piece)      9.45"
print "5                          Apple Pie                           1.29"
print "6                          Large Drink                         2.19"
print "7                          Large Fries                         2.29"


customer = raw_input ("Would you like to order? (If not type No)")
while customer != "No":

    while itemnum != -1: 
        itemnum = input("Enter the item you would like to purchase! ")
        quantity = input("How many of this item do you want? ")

        if itemnum == 1:
            foodprice = quantity * num1
            Totalprice1 = Totalprice1 + foodprice

        if itemnum == 2:
            foodprice = quantity * num2
            Totalprice2 = Totalprice2 + foodprice

        if itemnum == 3:
            foodprice = quantity * num3
            Totalprice3 = Totalprice3 + foodprice

        if itemnum == 4:
            foodprice = quantity * num4
            Totalprice4 = Totalprice4 + foodprice

        if itemnum == 5:
            foodprice = quantity * num5
            Totalprice5 = Totalprice5 + foodprice

        if itemnum == 6:
            foodprice = quantity * num6
            Totalprice6 = Totalprice6 + foodprice

        if itemnum == 7:
            foodprice = quantity * num7
            Totalprice7 = Totalprice7 + foodprice

    itemnum = input("Enter the item you would like to purchase! ")
    quantity = input("How many of this item do you want? ")
    subtotal = Totalprice1 + Totalprice2 + Totalprice3 + Totalprice4 + Totalprice5 + Totalprice6 + Totalprice7 
    billtax = subtotal * tax
    finalbill = subtotal + billtax        
    print "Your total bill without tax is... ", round(subtotal,2)
    print "Your total tax is... ", round(billtax,2)
    print "Your final bill is... ", round(finalbill,2)
    amtgiven = input ("How much do you want to pay with? ")
    change = amtgiven - finalbill
    print "Your change is... ", round(change,2)
    customer = raw_input ("Would you like to order? (If not type No)")

#输出

当我运行第二个程序时，输出如下:

Welcome to Virtual McDonald's!Would you like to order a food item
Item:                     Meal/tem:                          Price:
1                          Big Mac Meal                        4.87
2                          Quarter Pounder Meal                5.03
3                          Chicken Nuggets Meal (5 piece)      5.50
4                          ChickenNuggets Meal (10 piece)      9.45
5                          Apple Pie                           1.29
6                          Large Drink                         2.19
7                          Large Fries                         2.29
Would you like to order? (If not type No) yes
Enter the item you would like to purchase! 1
How many of this item do you want? 2
Enter the item you would like to purchase! 1
How many of this item do you want? 4
Your total bill without tax is...  9.74
Your total tax is...  0.55
Your final bill is...  10.29
How much do you want to pay with? 11
Your change is...  0.71
Enter the item you would like to purchase!

(输入几个菜单项后，程序停止运行循环并直接进入账单。此外，在账单之后，它不会询问用户是否是其他客户。)

当我运行第一部分时，输出如下:

Welcome to Virtual McDonald's!Would you like to order a food item
Item:                     Meal/tem:                          Price:
1                          Big Mac Meal                        4.87
2                          Quarter Pounder Meal                5.03
3                          Chicken Nuggets Meal (5 piece)      5.50
4                          ChickenNuggets Meal (10 piece)      9.45
5                          Apple Pie                           1.29
6                          Large Drink                         2.19
7                          Large Fries                         2.29
Enter the item you would like to purchase! 1
How many of this item do you want?4
Enter the item you would like to purchase! 2
How many of this item do you want?1
Enter the item you would like to purchase! -1
How many of this item do you want?-1
Your total bill without tax is...  24.51
Your total tax is...  1.38
Your final bill is...  25.89
How much do you want to pay with? 26
Your change is...  0.11

我希望第二部分输出第一部分输出的内容。除非它给了客户他/她的零钱，否则我希望它执行另一个循环，因此询问用户是否有另一个客户。如果用户输入"is"，则该程序将为另一个客户重新运行。只有当没有更多顾客时，用户才输入“否”来结束程序。 (我到python shell中复制了这些输出结果。右边的数字是我输入的数字。)

Answer 1

好的，有一些问题可以通过您的程序在语法和逻辑上进行修复。我继续修复它们，我将解释我做了什么以及为什么。首先，您需要另一个 while 循环来满足用户指定是否有其他客户排队的需求。我创建了一个新变量来处理新的 while 循环。这是代码:

nextcustomer = "yes"    
while nextcustomer != "no":
    amtgiven = 0
    change = 0
    quantity = 0
    foodprice = 0
    totalprice = 0
    billtax = 0
    finalbill = 0
    itemnum = 0

但是，在这个新循环中，我们需要添加一些变量，这些变量需要在每个客户之后重置。循环外的全局变量应该是那些不需要因客户而变化的变量，例如食品价格或税率。我们需要添加更改和总价以及这些内容，我在前面的代码中这样做了。

在所有其他事情发生之后，是否会有另一个客户的问题将进入第一个 while 循环，以便它知道是否再次迭代。这个问题在这里:

while nextcustomer != "no":
    (all of the code)
    nextcustomer = raw_input("Is there another customer? (yes or no) ")

我还在第二个 while 循环中添加了一些中断，否则它将继续迭代，而无法提示用户是否想要订购。

我所做的另一项更改是，我将所有 Totalprice1、Totalprice2...变量合并到一个变量 totalprice 中。为此，您只需要一个变量，因为您已经在自己的变量中定义了价格(num1, num2...)。每个选择下的计数器变量的代码如下所示:

totalprice += foodprice

这相当于总价格=总价格+食品价格。它只是更好的语法。另外，现在您甚至不需要 subtotal 变量。

我还在他们选择的数字的问题后面添加了一个 if 语句，如果他们输入 -1，则该数字将被选中，这样您就不必输入 -1 项的金额:

if itemnum == -1:
    break

我确信还有一些更改，我可能会回来编辑它以确保所有内容都得到解释，但这是编辑后的完整程序代码:

num1 = 4.87
num2 = 5.03
num3 = 5.50
num4 = 9.45
num5 = 1.29
num6 = 2.19
num7 = 2.29
tax = 0.0565
customer = 0
nextcustomer = "yes"
while nextcustomer != "no":
    amtgiven = 0
    change = 0
    quantity = 0
    foodprice = 0
    totalprice = 0
    billtax = 0
    finalbill = 0
    itemnum = 0
    print "Welcome to Virtual McDonald's!"
    print "Item:                     Meal/item:                          Price:"
    print "1                          Big Mac Meal                        4.87"
    print "2                          Quarter Pounder Meal                5.03"
    print "3                          Chicken Nuggets Meal (5 piece)      5.50"
    print "4                          ChickenNuggets Meal (10 piece)      9.45"
    print "5                          Apple Pie                           1.29"
    print "6                          Large Drink                         2.19"
    print "7                          Large Fries                         2.29"

    customer = raw_input ("Would you like to order? (If not type no)")
    while customer != "no":

        while itemnum != -1: 
            itemnum = input("Enter the item you would like to purchase! ")
            if itemnum == -1:
                break
            quantity = input("How many of this item do you want? ")

            if itemnum == 1:
                foodprice = quantity * num1
                totalprice += foodprice

            elif itemnum == 2:
                foodprice = quantity * num2
                totalprice += foodprice

            elif itemnum == 3:
                foodprice = quantity * num3
                totalprice += foodprice

            elif itemnum == 4:
                foodprice = quantity * num4
                totalprice += foodprice

            elif itemnum == 5:
                foodprice = quantity * num5
                totalprice += foodprice

            elif itemnum == 6:
                foodprice = quantity * num6
                totalprice += foodprice

            elif itemnum == 7:
                foodprice = quantity * num7
                totalprice += foodprice

        billtax = totalprice * tax
        finalbill = totalprice + billtax        
        print "Your total bill without tax is... ", round(totalprice,2)
        print "Your total tax is... ", round(billtax,2)
        print "Your final bill is... ", round(finalbill,2)
        amtgiven = input("How much do you want to pay with? ")
        change = amtgiven - finalbill
        print "Your change is... ", round(change,2)
        break
    nextcustomer = raw_input("Is there another customer? (yes or no) ")

这能解决您的问题吗？