Pastebin

class TreeNode:
    def __init__(self, data, parent=None, left = None, right = None):
        self.data   = data
        self.left   = left
        self.right  = right
        self.parent = parent

    def __repr__(self):
        return '%s(%s, %s)' % (self, repr(self.left), repr(self.right))

    def __str__(self):
        return self.data

class Tree:
    def __init__(self, root = None):
        self.root = root

    def __repr__(self):
        return '%s(%s, %s)' % (
                self.root, 
                repr(self.root.left), 
                repr(self.root.right)
                )


# Make some tree nodes
a = TreeNode('A')
b = TreeNode('B')
c = TreeNode('C')
d = TreeNode('D')

# Build tree structure
a.left  = b
a.right = c
b.left  = d

c.parent= a
b.parent= a
d.parent= b

# Assign root node
t = Tree(a)

print repr(t)


#              A
#             / \
#            B   C
#           /
#          D