How I can get back at the beginning of my code, when statement isn't meet?

Question

I've been doing my first calculator in Python and I have encountered small problem, let me show you a bit of my code:

fNum = input('Enter first number:' '\n')  # user gives numbers
sNum = input('Enter second number:' '\n')
if sNum.isalpha() or fNum.isalpha() is True:  # checking are they numbers
    print('You have to give me a number!')

How can I "return" to the beginning of the code and give user another chance to write down numbers? Because right now the program ends if letter or anything that isn't a number is inputted.

Thanks for help and sorry if this question is about something very easy, but I'm inexperienced yet.

Use a `while` loop! Check out some [Python tutorials!](http://www.tutorialspoint.com/python/) — miradulo, Mar 27 '15 at 17:11
Seconded. Something of the form `while sNum.isalpha() or fNum.isalpha()` — moarCoffee, Mar 27 '15 at 17:13

score 0 · Accepted Answer · answered Mar 27 '15 at 17:15

This technique is called validation, use a while loop until condition is broken:

num1 = input('Enter 1st number:') 
num2 = input('Enter 2nd number:')

# while both strings are not a bunch of digits 

while not (num1.isdigit() and num2.isdigit()):
    num1 = input('Enter 1st number:') 
    num2 = input('Enter 2nd number:')

How I can get back at the beginning of my code, when statement isn't meet?

1 Answers1