不能通过类型'str'的非int乘以序列不理解

Question

yen = 0.0067
bsp = 1.35
usd = 0.65
ero = 0.85

if choice == "2":
    Current_Currency = input("What currency do you want to exchange: Japenese Yen if so please type yen // British Sterling Pound please type bsp // US Dollers please Type usd // Euro please type ero.")
    if Current_Currency == "yen":
        amount = input("Type amount you wish to exchange")
        Future_Currency = input("What currency do you want to exchange into: Japenese Yen if so please type yen // British Sterling Pound please type bsp // US Dollers please Type usd // Euro please type ero.")
        New_Amount = Future_Currency * amount

我必须建立这个，显然我需要通过研究浮动，但我不知道如何实现它。

Answer 1

看起来你将变量名称与变量混淆了。 因为从用户获得的货币类型是字符串，所以除非您在其上调用eval，否则它不能用于引用变量。

new_amount = eval(future_currency) * amount

这样做的缺点是使用eval为用户提供了影响代码的可能方法。 相反，您可以使用字典。 字典将字符串映射到值，因此您可以获取变量声明：

yen = 0.0067
bsp = 1.35
usd = 0.65
ero = 0.85

把它们变成字典：

currencies = {'yen': 0.0067, 'bsp': 1.35, 'usd': 0.65, 'ero': 0.85}

使用此功能，您可以在字典中找到要查找的值。 不要忘记正确处理错误的用户输入！

currencies = {'yen': 0.0067, 'bsp': 1.35, 'usd': 0.65, 'ero': 0.85}

current_currency = raw_input()
future_currency = raw_input()
amount = int(raw_input())
// Check for errors in input here
new_amount = amount * currencies[future_currency] / currencies[current_currency]

Answer 2

这条线

Current_Currency = input("What currency do you want to exchange: Japenese Yen if so please type yen // British Sterling Pound please type bsp // US Dollers please Type usd // Euro please type ero.")

如果输入未知变量将抛出错误，并且Current_Currency将设置为用户提供的变量名称的值，因此该行

if Current_Currency == "yen":

不是真的需要。

yen = 0.0067
bsp = 1.35
usd = 0.65
ero = 0.85

Current_Currency = input("What currency do you want to exchange: Japenese Yen if so please type yen // British Sterling Pound please type bsp // US Dollers please Type usd // Euro please type ero.")
amount = input("Type amount you wish to exchange")
Future_Currency = input("What currency do you want to exchange into: Japenese Yen if so please type yen // British Sterling Pound please type bsp // US Dollers please Type usd // Euro please type ero.")
New_Amount =  Current_Currency / Future_Currency * amount