Input a number (generate error if not number)

Input a number, if it is not a number generate an error message.

while True:
    try:
        a = int(input("Input a number: "))
        break
    except ValueError:
        print("This is not a number. Try again...")
        print()

Output:

Input a  number: abc
This is not a number.  Try again...
Input a  number: 150

See also

https://www.w3resource.com/python-exercises/python-basic-exercise-113.php