(Python)自动售货机程序返回插入的错误金额

Question

我最近刚开始自学Python（3.5.1），并编写了一些基本程序。我正在尝试编写一个程序，允许用户最多购买3种产品。然而，我很难获得插入的总金额的正确值，我猜这是因为它一直在重新初始化自己。感谢您的帮助。另外，我的代码太复杂了吗？如果是，我该如何简化它

更新代码：

def main():
   displayPrices()
   purchaseItems()
def displayPrices():
   print("Item ID:tCost: ")
   print("1tt$1.25")
   print("2tt$0.75")
   print("3tt$0.90")
   print("4tt$0.75")
   print("5tt$1.50")
   print("6tt$0.75")
def purchaseItems():
   choice=""
   numItems=0
   totalCost=0
   totalReturned=0
   item=0
   change=0
   x=0
   money=float(input("Insert the amount of money you would like to input: $"))
   totalInserted=money
   while x < 3:
         item=int(input("nWhich item would you like to purchase?nIf you would like to quit, enter '0': "))
         if item == 1:
            cost = 1.25
         elif item == 2:
            cost = .75
         elif item == 3:
            cost = .90
         elif item == 4:
            cost = .75
         elif item == 5:
            cost = 1.50
         elif item == 6:
            cost = .75
         elif item == 0:
            print("Thank you for using our Vending Machine. Goodbye!")
            break
         else:
            print("Error. Please enter a valid Item ID [1-6]")
         if cost <= money:
               change = money - cost
               numItems+=1
               money=change
               totalCost=totalCost+cost
               totalReturned=change
               print("Thank you for purchasing Item " + str(item) + ". Your change is $" + str(round(change,2)) + ".n")
               x+=1
         else:
            moneyNeeded = cost - money
            print("Please enter an additional $" + str(moneyNeeded) + " to purchase your item.")
            newMoney=float(input("Insert the amount of money you would like to input: $"))
            totalInserted=money=money+newMoney
#  End of Loop
   print("Numbers of Items Purchased:", numItems)
   print("Total cost of all Items Purchased:", totalCost)
   print("Total amount of money inserted:", round(totalInserted,2))
   print("Total amount of change returned:", round(totalReturned,2))
main()

查看以下输出：
物料ID:成本：
1$1.25
2$0.75
3$0.90
4$0.75
5$1.50
6$0.75
插入您想要输入的金额：$0

你想购买哪种商品
如果要退出，请输入"0"：1
请额外输入1.25美元以购买您的商品
插入您想要输入的金额：$1.00

你想购买哪种商品
如果要退出，请输入"0"：2
感谢您购买物品2。您的零钱是0.25美元。

你想购买哪种商品
如果要退出，请输入"0"：1
请额外输入1.0美元以购买您的商品
插入您想要输入的金额：$1.0

你想购买哪种商品
如果要退出，请输入"0"：1
感谢您购买物品1。您的零钱是0.0美元。

你想购买哪种商品
如果要退出，请输入"0"：0
感谢您使用我们的自动售货机。再见
购买的物品数量：2
所有采购项目的总成本：2.0
插入的总金额：1.25---这是不正确的
返回的更改总量：0.0

Answer 1

我很惊讶这一行竟然运行时没有出错，但显然这是一个有效的构造：

totalInserted=money=money+newMoney

在该行中，totalInserted被分配了money的值。但是，当前可用的money与totalInserted不同。你真正想要的是：

money += newMoney
totalInserted += newMoney

如果你的代码太复杂，一个让它更简单的建议是将商品/价格关系存储在字典中：

prices = {1:1.25, 2:.75, ...}

然后稍后你可以这样做：

cost = prices[item]

您仍然需要首先检查item是0还是无效输入。您还有一个从未使用过的变量choice。

Answer 2

这里可能有一个解决方案。

def main():
   displayPrices()
   purchaseItems()

def displayPrices():
   print("Item ID:tCost: ")
   print("1tt$1.25")
   print("2tt$0.75")
   print("3tt$0.90")
   print("4tt$0.75")
   print("5tt$1.50")
   print("6tt$0.75")

def purchaseItems():
    money = float(input("How much money would you like to insert?"))
    moneyInserted = money
    items_sold = 0
    items = [1.25, .75, .9, .75, 1.5, .75]
    moneySpent = 0
    total_cost = 0
    x = 1
    while x != 0 and money > 0 and items_sold < 3:
        print("You have $" + str(money) + " left.")
        x = int(input("What item would you like to buy?"))
        if x == 0:
            pass
        elif x < 1 or x > 6:
            print("Please return a valid item number.")
        elif money >= items[x-1]:
            print("Thank you for buying item "+str(x)+".")
            money -= items[x-1]
            moneySpent += items[x-1]
            total_cost += items[x-1]
            items_sold += 1
        else:
            pass
    print("Number of items sold: " + str(items_sold))
    print("Money Inserted: " + str(moneyInserted))
    print("Amount of money spent: " + str(total_cost))
    print("Change amount: " + str(money))

main()