Linked_Lists.py

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

def push(head, data):
    node = Node(data)
    node.next=head
    return node

def build_one_two_three():
    lst = Node(3)
    lst = push(lst,2)
    lst = push(lst,1)
    return lst