Question

我似乎无法弄清楚如何获得坚持列表/元组的值之和

我尝试过使用键和其他一些方法，但都无法使用

#initialise variables
products = []
totalCost = 0.0


#input products and prices funtions
def getInput():
    product_name = input("What is the product?")
    product_price = input("What s the price?")

    return (product_name, product_price)

#collect input
for x in range(5):
    product = getInput()
    products.append(product)

#sort list
products.sort(key=lambda t: t[1], reverse=True)


#show list
def showTable():
    for x in range(5):
        print("Product Name | Price: ", products[x])

#calculate cheapest
def cheapestItem():
    print("The cheapest item in this list is: ", min(products, key = lambda t: t[1]))
    print("Congratulations you get this item free")

    #calculate total
    totalCost = sum(products[1]) - min(products[1])


#main
showTable()
cheapestItem()

我想获取价格的总和，并从该清单中减去最小的金额。

Answer 1

products = [('a',1),('b',2),('c',30),('d',10),('e',5)]

totalcost = sum([x[1] for x in products]) - min(products, key=lambda x:x[1])[1]

print(totalcost)

Answer 2

您有几个问题：

您没有数字，只有字符串：

def getInput():
    product_name = input("What is the product?")   # string
    product_price = input("What s the price?")     # string

    return (product_name, product_price)

修复（仅是价格输入部分）：

      while True:
          try: 
              product_price = int(input("What s the price?"))
              if product_price <= 0:
                  raise ValueError
              break
          except ValueError:
              print("Not a valid price")

请参见Asking the user for input until they give a valid response，以了解其他避免ValueError的方法。

只要您没有数字，'1000'就会小于'2'（字母比较）。

您最便宜的商品计算结果不符合预期：

即使您将产品固定为具有编号，您的totalCost也不起作用：

product[1] # this is the 2nd element of your list - not the price of it


def cheapestItem():
    print("The cheapest item in this list is: ", min(products, key = lambda t: t[1]))
    print("Congratulations you get this item free")

    #calculate total
    totalCost = sum(products[1]) - min(products[1])

修正（f.e。）：

   # assumes numbers in ("icecream", 42) - not strings
   sortedItems = sorted(products, lambda x:x[1])  # sort by price ascending

   minItem   = sortedItems[0]
   totalCost = sum(item[1] for item in sortedItems[1:])   # don't calc the lowest value
   totalCost = sum(products[1]) - min(products[1])

使用min()也可以，但是通过排序，您可以使用列表切片对除最低点以外的所有部分求和。如果您有巨大列表-min()更为合适：

   minItem = min(products, lambda x:x[1])
   total = sum(item[1] for item in products) - minItem[1]  # reduced by minItems cost

我修复了代码，以使用提供给函数的参数，而不使用全局参数-也不需要min（）产品列表，因为无论如何您都要对其进行排序-您可以简单地切掉最低的项目并扣除其价值：

固定代码和示例输入：

def getInput():
    product_name = input("What is the product? ")
    while True: 
        try:
            # whole number prices assumed, else use float( input ( ... ))
            product_price = int(input("What s the price? "))
            if product_price <= 0:
                raise ValueError
            break
        except ValueError:
            print("Wrong input - prices must be greater 0 and whole numbers")

    return (product_name, product_price)

def showTable(p):
    for x in p:
        print("Product Name | Price: ", x[0],x[1])

def cheapestItem(p):
    # assumes sorted list of items in p
    print("The cheapest item in this list is: ", p[-1])
    print("Congratulations you get this item free")

    #calculate total
    totalCost = sum(i[1] for i in p[:-1])
    print("Total Cost:", totalCost, "You saved:", p[-1])


products = [] 
for x in range(5):
    product = getInput()
    products.append(product)

# sort list - cheapestItem(..) needs a sorted input to work
products.sort(key=lambda t: t[1], reverse=True)

showTable(products)
cheapestItem(products)

输出：

What is the product? apple
What s the price? 22
What is the product? pear
What s the price? 11
What is the product? kiwi
What s the price? 5
What is the product? pineapple
What s the price? no idea
Wrong input - prices must be greater 0 and whole numbers
What s the price? 100
What is the product? gears
What s the price? 1

Product Name | Price:  pineapple 100
Product Name | Price:  apple 22
Product Name | Price:  pear 11
Product Name | Price:  kiwi 5
Product Name | Price:  gears 1
The cheapest item in this list is:  ('gears', 1)
Congratulations you get this item free
Total Cost: 138 You saved: ('gears', 1)

Answer 3

尝试一下：

#initialise variables
products = []
totalCost = 0.0


#input products and prices funtions
def getInput():
    product_name = input("What is the product?")
    product_price = int(input("What s the price?"))

    return (product_name, product_price)

#collect input
for x in range(5):
    product = getInput()
    products.append(product)

#sort list
products.sort(key=lambda t: t[1], reverse=True)


#show list
def showTable():
    for x in range(5):
        print("Product Name | Price: ", products[x])

#calculate cheapest
def cheapestItem():
    print("The cheapest item in this list is: ", min(price))
    print("Congratulations you get this item free")


price = []
for i in range(len(products)):
    price.append(products[i][1])

totalCost = sum(price) - min(price)
print(totalCost)

#main
showTable()
cheapestItem()

您不能将元组列表传递给sum（）。它需要一个数字列表。

Answer 4

如果我说对了，这应该可以工作：

products.remove(min(products))
print(sum(products))

列表/元组故障内的值总和

4 个答案: