reverse-a-doubly-linked-list.py

"""
 Reverse a doubly linked list
 head could be None as well for empty list
 Node is defined as
 
 class Node(object):
 
   def __init__(self, data=None, next_node=None, prev_node = None):
       self.data = data
       self.next = next_node
       self.prev = prev_node

 return the head node of the updated list 
"""

def Reverse(head):
    prev = None
    node = head
    
    while node is not None:
        buf = node.next
        node.next = prev
        prev = node
        node = buf
        
    head = prev
    return head