tree.py

class Node:
    def __init__(self, n):
        self.n = n
        self.left = None
        self.right = None

class BinarySearchTree:
    def __init__(self, node=None):
        self.head = node

    def add(self, node):
        if self.head == None:
            self.head = node
        else:
            if node.n > self.head.n:
                self.head.right = BinarySearchTree(self.head.right).add(node).head
            else:
                self.head.left = BinarySearchTree(self.head.left).add(node).head

        return self

    def search(self, n):
        if self.head == None:
            return None

        if self.head.n == n:
            return self.head
        elif n > self.head.n:
            return BinarySearchTree(self.head.right).search(n)
        else:
            return BinarySearchTree(self.head.left).search(n)

    def print_in_order(self):
        if self.head != None:
            BinarySearchTree(self.head.left).print_in_order()
            print self.head.n
            BinarySearchTree(self.head.right).print_in_order()