def is_digit(x):if type(x) == int:return Trueelse:return Falsedef main():shape_opt = input('Enter input >> ')while not is_digit(shape_opt):shape_opt = input('Enter input >> ')else:print('it work')if __name__ == '__main__':main()

So when the user input a value that is not an integer, the system will repeat the input(). Else, it does something else. But it won't work, may I know why?

Check this. Input always returns a string. So isdigit() is better to use here. It returns True if all characters in a string are digits and False otherwise.

return x.isdigit() will evaluate to True/False accordingly, which will be returned

def is_digit(x):return x.isdigit()def main():shape_opt = input('Enter input >> ')while not is_digit(shape_opt):shape_opt = input('Enter input >> ')else:print('it work')    if __name__ == '__main__':main()