根据堆栈跟踪， r 是 str .您应该只使用数字，因此为了进行操作，请将r转换为 float (因为它处理十进制数字)

According to the stacktrace, r is a str. You should work with numbers only, so in order to do the operation, convert r to float (as it deals with decimal numbers)

r = float(input("Enter annual interest amount. (decimal) "))

编辑

好吧，让我们停下来思考.当您使用 python 3 时，输入函数会将您输入的值存储为字符串(即文本).您希望它们成为数字.

Edit

Ok, lets stop and think. As you are using python 3 , the input function will store the value you input as a string (i.e. as text). You want them to be numbers.

因此，您必须将所有内容都转换为数字，以便能够相乘，除等.例如，"a"/"b" 是什么意思?那么"a1"/"b2" 呢?甚至是"1"/"2" ?他们没有道理.但是， 1/2 是有意义的.区别在于，我们在前三个示例中处理文本，而在最后一个示例中处理数字.

So, you have to convert everything to numbers so that you are able to multiply, divide etc. For example, what does "a"/"b" means? And what about "a1"/"b2"? Or even "1"/"2"? They make no sense. However, 1/2 makes sense. The difference is that we are dealing with text in the first 3 examples, and with numbers in the last example.

要使其正常工作，您应该将所有内容都转换为 int 或 float .这些 types 是数字，您可以不用担心就可以对它们进行数学运算.

To make it work, you should convert everything either to int or to float. These types are numbers, and you can do mathematical operations with them without worries.