Question

我试图在for循环中获取乘法来处理下面的代码：

#products list and it's values per unity
tomato = 2
potato = 3
carrot = 1
pricePaid = int()

print("Welcome to my grocery shop!\n")

productList = ["Potato", "Tomato", "Carrot"]

print("What will you want today?\n""We have:")
print(*productList, sep=', ')
product = input("What will it be? ")

quantity = int(input("And how many do you want? "))

for productChoice in product:
    if productChoice == "Potato":
        pricePaid = quantity * potato
    elif productChoice == "Tomato":
        pricePaid = quantity * tomato
    elif productChoice == "Carrot":
        pricePaid = quantity * carrot

print("Here's your bag with {0} {1}s. The total is ${2:.2f}.".format(quantity, product, pricePaid))

但我得到的结果为0.00美元我的结果应该是数量* productPrice：

"Here's your bag with 1 Tomatos. The total is $0.00."

为什么失败？我在这里缺少什么？

我正在使用Python 3.x

提前致谢！

Answer 1

您正在迭代输入中的字符，并设置每次支付的价格。没有必要进行迭代，因为product不会改变。删除for循环就可以了。您还需要删除对productChoice的引用，因为它（字面上）没有任何意义。

#products list and it's values per unity
tomato = 2
potato = 3
carrot = 1
pricePaid = int()

print("Welcome to my grocery shop!\n")

productList = ["Potato", "Tomato", "Carrot"]

print("What will you want today?\n""We have:")
print(*productList, sep=', ')
product = input("What will it be? ")

quantity = int(input("And how many do you want? "))

if product == "Potato":
    pricePaid = quantity * potato
elif product == "Tomato":
    pricePaid = quantity * tomato
elif product == "Carrot":
    pricePaid = quantity * carrot

print("Here's your bag with {0} {1}s. The total is ${2:.2f}.".format(quantity, product, pricePaid))

Answer 2

这导致了您的问题：

for productChoice in product:
    if productChoice == "Potato":
        pricePaid = quantity * potato
    elif productChoice == "Tomato":
        pricePaid = quantity * tomato
    elif productChoice == "Carrot":
        pricePaid = quantity * carrot

如果我们快速改变这一点，我们可以看到原因

for productChoice in product:
    print(productChoice)

产品为“番茄”的输出

T
o
m
a
t
o

当你实际上不想要这种行为时，你在这里做的是迭代字符串product中的每个字符。解决问题的方法就是删除for循环，仅保留选择。

这就是你所需要的：

if product == "Potato":
    pricePaid = quantity * potato
elif product == "Tomato":
    pricePaid = quantity * tomato
elif product == "Carrot":
    pricePaid = quantity * carrot

希望这有帮助！

Answer 3

您正在迭代producChoice中的字母。

在循环中添加print(productChoice)以观察发生的情况。由于没有一个字母等于您的某个产品，因此不会触发任何条件语句，并且pricePaid将保持其原始值int() == 0。

根本不需要for循环，所以只需删除它。

Answer 4

这是使用词典的改进代码。单单词典值得研究，以使代码更轻松。基本上，字典由持有值（例如1）的键（例如番茄）组成。您可以使用.get（）。

获取这些值

#products list and it's values per unity
prices = dict(tomato=2,potato=3,carrot=1)

product = input('''\
Welcome to my grocery shop!
What will you want today?
We have: {}
What will it be?
'''.format(', '.join(prices.keys()))).lower()

quantity = int(input("And how many do you want? "))

pricePaid = prices.get(product,0) * quantity

if pricePaid:
    print("Here's your bag with {0} {1}s. The total is ${2:.2f}."
          .format(quantity, product, pricePaid))
else:
    print("Error with input!")

我在python中的乘法不起作用

4 个答案: