tree.py

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

    def __str__(self):
        s = ''
        if self.left is not None:
            s += str(self.left)
        s += str(self.val) + ' '
        if self.right is not None:
            s += str(self.right)
        return s

    def __repr__(self):
        return str(self)


def insert(n, val):
    if val > n.val:
        if n.right is None:
            n.right = Node(val)
        else:
            insert(n.right, val)
    else:
        if n.left is None:
            n.left = Node(val)
        else:
            insert(n.left, val)

node = Node(5)
insert(node, 8)
insert(node, 3)
insert(node, 4)
insert(node, 6)
insert(node, 7)
insert(node, 0)
print node