https://leetcode.com/problems/rotate-list/

rotateList.py

class Solution:
    def rotateRight(self, head: ListNode, k: int) -> ListNode:
        if not head: return None
        
        # get the length of the list
        length, current = 0, head
        while current:
            length+=1
            current = current.next
        k%=length
        
        if not k: return head
        
        # mod k so k < length of list
        current, front = head, head
        while k:
            front = front.next
            k-=1
        
        # advance front by k
        while front.next:
            current = current.next
            front = front.next
        
        # splice and return the new head
        newHead = current.next
        current.next = None
        front.next = head
        return newHead