Recursion seems to iterate one last time how can I fix this code?

I am attempting to check if a string is a palindrome or not( reads the same forwards and backwards )

I am having trouble understanding why the output is throwing the error that the variable has not been assigned after the code that says it has been assigned. I have a base case and a recursive case.

I also need to use only one return.

def is_palindrome(s)
    if len(s)<=1: # if we have reached the end of the string
        print("is palindrome")
        palindrome = True
        print("set palindrome to true")
        
    elif len(s)>1:
        print("length not 1, checking again")
        if s[0] == s[-1]:
            print("leftmost = rightmost")
            newstring = s[1:]
            newstring = newstring[:-1]
            s = newstring
            is_palindrome(s)
        else: 
            print("not palindrome")
            palindrome = False
        
    return palindrome

Output:

length not 1, checking again
leftmost = rightmost
length not 1, checking again
leftmost = rightmost
length not 1, checking again
leftmost = rightmost
is palindrome
set palindrome to true

Error:

   Traceback (most recent call last):   
    line 16, in <module>
            print(is_palindrome(s))   
    line 134, in is_palindrome
            is_palindrome(s)   
    line 134, in is_palindrome
            is_palindrome(s)   
    line 139, in is_palindrome
            return palindrome UnboundLocalError: local variable 'palindrome' referenced before assignment

EDIT:
I now have this code however it seems as though it is returning true regardless

CODE:

palindrome = True
#BASE CASE
if len(s)>1:
    print("length not 1, checking again")
    if s[0] == s[-1]:
        print("leftmost = rightmost")
        newstring = s[1:]
        newstring = newstring[:-1]
        s = newstring
        is_palindrome(s)
    else: 
        print("not palindrome")
        palindrome = False
    
return palindrome

OUTPUT:

length not 1, checking again
leftmost = rightmost
length not 1, checking again
leftmost = rightmost
length not 1, checking again
not palindrome
True

The issue is that you're assuming the palindrome variable is carried throughout the recursion, but it is a different piece of data each time recursion starts. So if you only follow the very first layer:

def is_palindrome(s)
    if len(s)<=1: # if we have reached the end of the string
    #    print("is palindrome")
    #    palindrome = True
    #    print("set palindrome to true")
        
    elif len(s)>1:
        print("length not 1, checking again")
        if s[0] == s[-1]:
            print("leftmost = rightmost")
            newstring = s[1:]
            newstring = newstring[:-1]
            s = newstring
            is_palindrome(s)
    #    else: 
    #        print("not palindrome")
    #        palindrome = False
        
    return palindrome

you get this. I commented out everything that doesn't run on the first layer, as you can see palindrome is never set. To accomplish what you want, I would take the line:

        if s[0] == s[-1]:
            print("leftmost = rightmost")
            newstring = s[1:]
            newstring = newstring[:-1]
            s = newstring
            is_palindrome(s)

and write it like this:

        if s[0] == s[-1]:
            print("leftmost = rightmost")
            newstring = s[1:]
            newstring = newstring[:-1]
            s = newstring
            palindrome = is_palindrome(s)

A key problem is this line:

is_palindrome(s)

You know is_palindrome() returns a value, but you've ignored it. That returned value you ignored is key to solving the problem. Here's a simplified logic for the problem:

def is_palindrome(s):
	palindrome = False  # assume not a palindrome

	if len(s) <= 1:  # we have reached a minimal string
		palindrome = True  # it's palindrome
	elif s[0] == s[-1]:  # if leftmost == rightmost
		palindrome = is_palindrome(s[1:-1])  # recurse on "inner" string

	return palindrome

if is_palindrome("9609457639843489367549069"):
	print("is palindrome")

Since this code doesn't handle case, white space and punctuation, it's not as useful for language palindromes as it is for things like numeric palindromes.