palindrome.py

def measure_palindrome(prefix,postfix):
    i=0
    while i<len(prefix) and i<len(postfix):
        if prefix[-i-1]!=postfix[i]:
            break
        i+=1
    return i

def longest_palindrome(s):
    longest=""
    for i in range(len(s)-1):
        rlen = measure_palindrome( s[:i], s[i+1:])
        if rlen>0 and (rlen*2+1)>len(longest):
            longest=s[i-rlen:i+rlen+1]
    return longest

assert(longest_palindrome("aabcdcb")=="bcdcb")
assert(longest_palindrome("bananas")=="anana")
assert(longest_palindrome("aba")=="aba")
assert(longest_palindrome("ab")=="")