尝试用Python为ebay卖家制作应用程序

Question

尝试制作一个应用程序，减去所有在易趣上出售的物品的费用

NetSale = 0
ListFee = 0
PayPalFee = 0
ShippingFee = 0

def int_or_float(i):
    try:
        return int(i)
    except ValueError:
        return float(i)


NetSale = input("What is the Net Sale? ")
ListFee = input("What is the List Fee? ")
PayPalFee = input("What is the PayPal Fee? ")
ShippingFee = input("What is the Shipping Cost? ")

int_or_float(NetSale)
int_or_float(ListFee)
int_or_float(PayPalFee)
int_or_float(ShippingFee)

Profit = NetSale-ListFee

print(Profit)

当我运行应用程序时，我得到一个类型错误，因为它试图减去两个字符串。如果这些变量包含int或float，如何使其相减

Answer 1

可以在请求用户输入时进行int/float的转换。下面的代码应该可以做到这一点

NetSale = 0
ListFee = 0
PayPalFee = 0
ShippingFee = 0

def int_or_float(i):
    try:
        return int(i)
    except ValueError:
        return float(i)


NetSale = int_or_float(input("What is the Net Sale? "))
ListFee = int_or_float(input("What is the List Fee? "))
PayPalFee = int_or_float(input("What is the PayPal Fee? "))
ShippingFee = int_or_float(input("What is the Shipping Cost? "))

Profit = NetSale-ListFee

print(Profit)

Answer 2

在Python中，将不可变对象传递给函数将按值传递，而不是按引用传递。在int_or_float()函数中将值强制转换为int()或float()，但不会在代码的主流中捕获它。因此，NetSale变量不会被int_or_float()函数修改。它仍然是一根弦。只需在函数调用之后捕获它：

NetSale = int_or_float(NetSale)
ListFee = int_or_float(ListFee)
PayPalFee = int_or_float(PayPalFee)
ShippingFee = int_or_float(ShippingFee)