Python for the absolute beginner

[edperez7]

I need help with this challenge I have in a book I'm reading. I can't really understand the questions.

Improve the function ask_number()so that the function can be
called with a step value. Make the default value of step 1.

Here's the function

def ask_number(question, low, high):
    """Ask for a number within a range."""
    response = None
    while response not in range(low, high):
        response = int(input(question))
    return response

[bvdet]

def ask_number(question, low, high, step=1):
    response = None
    while response not in range(low, high, step):
        response = int(input(question))
    return response

if __name__ == "__main__":
    print ask_number("Enter an even number between 0 and 20", 0, 21, step=2)