Python recursive function enter -

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• python recursion list returns none 1 answer

ps: question marked duplicate , there answer. thing is, question not same other one. in problem, know code wrong. im asking why wrong.

this problem on udacity asked solve:

define procedure is_palindrome, takes input string, , returns boolean indicating if input string palindrome.

hint:

base case: '' => true

recursive case: if first , last characters don't match => false

if match, middle palindrome?

def is_palindrome(s):     if s=='':         return true     else:         if s[0]!=s[-1]:             return false         else:             s=s[1:-1]             is_palindrome(s) 

and 3 input cases try:

print is_palindrome('') #>>> true print is_palindrome('abab') #>>> false print is_palindrome('abba') #>>> true 

if leave code that, return none case 'abba'. can fixed changing last line of function into

return is_palindrome(s[1:-1]) 

may ask why return matter? without return, shouldn't run function is_palindrome() on again , again?

even without return, shouldnt run function is_palindrome() on again , again?

sure -- it'll run on , over, won't return useful, you'll never see result. because first is_palindrome call return none independent of return values of recursing calls is_palindrome (none python's default when don't specify return value).