"""
 euler4.py

 problem 4 from projecteuler.net:

 largest numeric palindrome produce 
 of two three digit numbers.

"""

def is_palindrome(n):
    """ True if n is a palindrome number
        >>> is_palindrome(121)
        True
        >>> is_palindrome(123)
        False
    """
    n_str = str(n)
    return n_str[::-1] == n_str

def main():
    biggest = 0
    best_a = 0
    best_b = 0
    for a in range(100, 1000):
        for b in range(a, 1000):
            n = a * b
            if is_palindrome(n):
                if n > biggest:
                    biggest = n
                    best_a = a
                    best_b = b
    print("answer is a={}, b={}".format(best_a,
                                        best_b))

if __name__ == '__main__':
    import doctest
    doctest.testmod()
    main()