# functions
def float_check(question):
    """checks users enter a float"""

    error = "Oops - please enter a number more than zero."

    while True:
        response = input(question).lower()

        # check for exit code
        if response == "xxx":
            return response

        try:
            # change response to an integer and check it's more than 0
            response = float(response)

            if response > 0:
                return response
            else:
                print(error)

        except ValueError:
            print(error)

# main routine

# testing loop
while True:
    my_float = float_check("Please enter a number: ")