Palindrome Linked List in Python with O(1) Extra Space (O(n) time)

palindrome.py

class ListNode:
   def __init__(self, val=0, next = None):
      self.next = next
      self.val = val

class Solution:
     def isPalindrome(self, head:ListNode) -> bool:
        fast = head
        slow = head
        #find middle
        while fast and fast.next :
           fast = fast.next.next
           slow = fast.next
        # reverse second half
        prev = None
        while slow:
            temp = slow.next
            slow.next = prev
            prev = slow
            slow  = temp


        #check palindrome
        left, right = head,prev
        while right :
            if left.val == right.val : 
                return False
            
            left = left.next 
            right = right.next
        return True
        
def make_list(elements):
   head = ListNode(elements[0])
   for element in elements[1:]:
      ptr = head
      while ptr.next:
         ptr = ptr.next
      ptr.next = ListNode(element)
   return head



head = make_list([1,2,3,2,1])
ob1 = Solution()
print(ob1.isPalindrome(head))   # True