oops.py

class node:
    def __init__(self):
        self.data = None
        self.next = None

class linked_list:
    def __init__(self):
        self.current_node=None
    
    def add_node(self,data):
        new_node = node()
        new_node.data = data
        new_node.next = self.current_node
        self.current_node = new_node
    
    def list_print(self):
        node = self.current_node
        while node:
            print node.data
            node=node.next
    def reverse(self):
        current = self.current_node
        prev = None
        next = None

        while current:
            next = current.next
            current.next = prev
            prev = current
            current = next     
        self.current_node = prev
    
    def print_middle(self):
        hare = self.current_node
        tort=self.current_node
        temp = tort

        while( hare and  hare.next ):
            prev = tort
            hare = hare.next.next
            tort = tort.next
        print tort.data    
        
            
        
ll = linked_list()
ll.add_node(1)
ll.add_node(2)
ll.add_node(3)
ll.add_node(4)
ll.add_node(5)
ll.list_print()
print 'After reverse '
ll.reverse()
ll.list_print()
print 'Middle value is '
ll.print_middle()