def main():
    highest_number = prompt_for_end_value()
    list_of_possible_primes = []
    prime_values = []

    for x in range(2, highest_number):
        list_of_possible_primes.append(x)

    list_of_possible_primes.reverse()

    while list_of_possible_primes:
        is_prime = list_of_possible_primes.pop()
        prime_values.append(is_prime)

        print(str(is_prime) + ' is a prime number')
        list_of_possible_primes = [maybe_factor
                                   for maybe_factor in list_of_possible_primes
                                   if ((maybe_factor % is_prime) != 0)]

    print('A list of all prime number has been returned, and printed below')
    print(prime_values)
    return prime_values


def prompt_for_end_value():
    return_value = None
    while not return_value:
        possible_return = eval(input('Please input the highest number to evaluate for primes:'))
        if not isinstance(possible_return, int):
            print('Input must be a whole number.')
        elif possible_return < 2:
            print('End Value can not be less then 2')
        else:
            return_value = possible_return

    return return_value


if __name__ == '__main__':
    main()