我在运行程序“ ValueError：int（）的基数为10的无效文字：”时遇到此错误：

Question

i am attempting to build a composite function calculator, but I'm running into some issues.

import math

xval = input(int("what is the value of X?"))

fval = input(str("what is the value of f?"))

gval = input(str("what is the value of f?"))

this is the bit of code that isn't working. For the "xval" variable i keep on getting the error message

ValueError: invalid literal for int() with base 10: 'what is the value of X?'

I've looked around online, but I can't find any issues with my code.

Answer 1

You have to first execute input and then int to cast the result into an integer number.

Otherwise you are trying to convert a text into an integer

xval = int(input("what is the value of X?"))

In the other lines, the str is redundant, but is it really what you want? I mean to me it looks like fval and gval should also be numbers.

Ah, and the text for gval should be "what is the value of g "

Also take in account that int will convert your inputs to integers, if you need decimal numbers consider using float()

Explanation:

Your original line input(int("what is the value of X?")) basically does the following steps:

1. Creates the string "what is the value of X?"
2. Tries to convert this string to an integer number (and fails)
3. Supposing point 2 doesn't fail (which does), then it will execute input giving an integer as text (and failing again) and storing your input as a string. As a result your variable xval would be a string (which is not what you want)

Instead, what you want is to first execute input and convert the value that you type into an integer, so you have to execute:

xval = int(input("what is the value of X?"))

Note that if you input a string, then the cast into int() will fail, you might want to use try and catch a possible exeption.

Answer 2

If you are using Python3.x, Python 3.x doesn't evaluate and convert the data type, you have to explicitly convert to int

x = int(input("what is the value of X?"))

If you are using Python2.x, you need to do like this:

x = input("what is the value of X?")

You can then check the type of x using type(x), you will get <type 'int'>