I quickly checked my naive solution against cpython 2.7 and pypy-2.0-beta1 and it seems to be at least as fast as your code: ispalindrome = lambda a: a[::-

I quickly checked my naive solution against cpython 2.7 and pypy-2.0-beta1 and it seems to be at least as fast as your code: ispalindrome = lambda a: a[::-1] == a