# Palindrome Function
def is_palindrome(s):
    if not isinstance(s, str) or len(s) == 0:
        return False
    s = ''.join(e for e in s if e.isalnum()).lower()
    left, right = 0, len(s)-1
    while left < right:
        if s[left] != s[right]:
            return False
        left += 1
        right -= 1
    return True