python 判断是否为回文

[lionzhnn]

print 'kill game by input end'
while 1:
s=input("input string:")
if s== 'end':
break;
s1='';
index=0;
l=len(s);
while index<l:
s1=s1+s[l-index-1];
index=index+1;
if s1==s:
print 'the string is a palindrome'
else:
print 'the string is not a palindrome'