reverse a singly linked list

reverse_single_linked_list.py

#!/usr/bin/env python

class Node: 
    data = None
    next = None
    def __init__(self,lndata):
        self.data=lndata

class List: 
    size = 0
    head = None
    tail = None
    def __init__(self): 
        self.head = None
        self.tail = None
        self.size = 0
        
    def insert(self,value):  
        newnode = Node(value) 
        if self.head is None:
            self.head = newnode  
            self.tail = newnode
            self.tail.nextnode = None
            self.size = self.size + 1
        else:
            temp_node = self.head 
            while temp_node.next is not None: 
                temp_node = temp_node.next
            temp_node.next = newnode 
            self.tail = newnode
            self.tail.next = None 
            self.size = self.size + 1 

    def toString(self):
        if self.size == 0: 
            print "[]"
        else:
            temp_node = self.head
            print "[",
            while (temp_node is not None):
                print temp_node.data,
                temp_node = temp_node.next
            print "]"

    def reverse(self):
        pCurrent = self.head
        pNext    = pCurrent.next
        pNNext   = pNext.next
        while pNext.next is not None:
            if pCurrent == self.head:
                pCurrent.next = None
            pNext.next  = pCurrent
            pCurrent    = pNext
            pNext       = pNNext
            pNNext      = pNext.next
        pNext.next = pCurrent
        self.head = pNext

if __name__=='__main__':
    link = List()
    link.insert(1)
    link.insert(2)
    link.insert(3)
    link.insert(4)
    link.toString()
    link.reverse()
    link.toString()