I am making a function to detect input types in Py

Question

So I am making a prime number detector as a project. I’m VERY new to programming and my friend showed me a little python. I want to make a function that detects if the user puts in a number for the input (like 5,28,156,42,63) and if the put in something else (like banana,pants,or cereal) to give them a custom error saying "Invalid Number. Please Try Again" and then looping the program until they put in a number.

Please help me make this work.

def number_checker():
    user_number = int(input('Please enter a Number: '))
    check = isinstance(user_number, int)
    if check == True:
        print ('This is a number')
    if check == False:
        print ('This is not a number')

Answer 1

Try following:

def number_checker():
    msg = 'Put your number > '
    while True:
        user_input = input(msg)
        correct = user_input.isdigit()
        if correct:
            print("This is an integer")
            return  # here you can put int(user_input) 
        else:
            print("This is not an integer")
            msg = 'You typed not integer. Try again.> '

if __name__ == '__main__':
    number_checker() 

And it's also good rule give names for your functions as verbs according to what they do. For this one, I would give, for example def int_input or something.

Answer 2

1) Casting input to int would raise an exception if the input string cannot be converted to int.

user_number = int(input('Please enter a Number: '))
              ^^^

2) It does not make sense to cross-verify user_number with int instance as it would already be int
3) You can try

def number_checker():                          
    while not input("enter num: ").isdigit():  
        print("This is not a number")          
    print("This is a number")                  
number_checker()