如何从用户输入中捕获浮点值以获取浮点值的总和

Question

任务是：编写代码，在列表中搜索客户订购的加载项名称。编写打印加载项名称和价格或错误消息的代码，然后编写打印总订单成本的代码。使用以下数据执行程序并验证输出是否正确：CreamCaramelWhiskeychocolateChocolateCinnamonVanilla我已经执行了分配的主要部分，但不明白如何捕获先前输入的值以求和/相加。我的代码：# Declare variables.NUM_ITEMS = 5 # Named constant# Initialized list of add-insaddIns = ["Cream", "Cinnamon", "Chocolate", "Amaretto", "Whiskey"]# Initialized list of add-in pricesaddInPrices = [.89, .25, .59, 1.50, 1.75] # Flag variableorderTotal = 2.00  # All orders start with a 2.00 charge# Get user input# addIn = ""addIn = input("Enter coffee add-in or XXX to quit: ")# Write the rest of the program here.while addIn != "XXX":    foundIt = False    for i in range(0, len(addInPrices)):        price = addInPrices[i]        product = addIns[i]        if addIn == product:             foundIt = True            break    if foundIt == True:        print("{} Price is ${}".format(product,price))    else:         print("Sorry, we do not carry that.")    addIn = input("Enter coffee add-in or XXX to quit: ")# MY COMMENT --- Want to create new list from input above when foundIT == True and sum total to print out total order cost.    newList=[]  #Create new list to grab values when foundIt == True    while foundIt == True:        addCost=price        newList.extend(addCost)        foundIt == True        break    else:        foundIt == False    print(newList)print("Order Total is ${}".format(orderTotal))我发现我一直在尝试迭代浮点数（例如addCost，price等）或迭代不允许的“布尔”。我是否应该在代码前面的列表中捕获用户的输入，以便为练习的最后一步求和？除了创建一个列表来解决练习之外，我还应该考虑其他事情吗？如果有，请分享。

Answer 1

而不是extend在您的清单上，您实际上想要append该项目。extend将另一个列表连接到您的列表中，向列表中append添加一个值。

但实际上，我们根本不需要这个列表来做你想做的事情。相反，我们可以在考虑项目时将价格添加到总数中。我们也可以在这里打印价格，只依靠foundIt标志输出错误信息

# Declare variables.

NUM_ITEMS = 5 # Named constant

# Initialized list of add-ins

addIns = ["Cream", "Cinnamon", "Chocolate", "Amaretto", "Whiskey"]

# Initialized list of add-in prices

addInPrices = [.89, .25, .59, 1.50, 1.75]

# Flag variable

orderTotal = 2.00  # All orders start with a 2.00 charge

# Get user input

# 

addIn = ""

addIn = input("Enter coffee add-in or XXX to quit: ")

# Write the rest of the program here.

while addIn != "XXX":

    foundIt = False

    for i in range(len(addIns)):

        if addIn == addIns[i]:

            print("Found match!")

            orderTotal += addInPrices[i]

            foundIt = True

            print("{} Price is ${}".format(addIns[i],addInPrices[i]))

            addIn = input("Enter coffee add-in or XXX to quit: ")

            continue

    print("Sorry, we do not carry that.")

    addIn = input("Enter coffee add-in or XXX to quit: ")

print("Order Total is ${}".format(orderTotal))

Answer 2

而不是 addcost 是可变的，它应该是列表。扩展运算符仅适用于列表。

# Declare variables.

NUM_ITEMS = 5 # Named constant

# Initialized list of add-ins

addIns = ["Cream", "Cinnamon", "Chocolate", "Amaretto", "Whiskey"]

# Initialized list of add-in prices

addInPrices = [.89, .25, .59, 1.50, 1.75]

 # Flag variable

orderTotal = 2.00  # All orders start with a 2.00 charge

# Get user input

# 

addIn = ""

addIn = input("Enter coffee add-in or XXX to quit: ")

# Write the rest of the program here.

while addIn != "XXX":

    foundIt = False

    for i in range(0, len(addInPrices)):

        price = addInPrices[i]

        product = addIns[i]

        if addIn == product: 

            foundIt = True

            break

    if foundIt == True:

        print("{} Price is ${}".format(product,price))

    else: 

        print("Sorry, we do not carry that.")

    addIn = input("Enter coffee add-in or XXX to quit: ")

# MY COMMENT --- Want to create new list from input above when foundIT == True and sum total to print out total order cost.

    newList=[]  #Create new list to grab values when foundIt == True

    while foundIt == True:

        addCost=[price]

        newList.extend(addCost)

        foundIt == True

        break

    else:

        foundIt == False

    print(newList)

print("Order Total is ${}".format(orderTotal+sum(addCost)))