Code to reverse a singly linked list

reverse_linked_list.py

class Solution:
    def reverseList(self, head: ListNode) -> ListNode:
      # check if head exists or if there are at least 2 nodes.
        if head is None or head.next is None:
            return head
        else:
          
            current_node = head
            while current_node.next is not None:
              
                # get next node
                next_node = current_node.next
                
                # move current_node forward
                current_node.next = next_node.next
                
                # push next_node to front of linked list
                next_node.next = head
                
                # reassign head
                head = next_node
                
            return head