Finds sf and checks if number and more than 0

03_find_scale_factor.py

# Functions go here
def num_check(question):
    error = "Please enter a number that is more than zero"

    valid = False
    while not valid:
        try:
            response = float(input(question))

            if response <= 0:
                print(error)
            else:
                return response

        except ValueError:
            print(error)


# Main Routine goes here

serving_size = num_check("What is the recipe serving size? ")
desired_size = num_check("How many servings are needed? ")

scale_factor = desired_size / serving_size

print("Scale factor: {}".format(scale_factor))