btree.py

class BTree:
    def __init__(self,value):
        self.left=None
        self.data=value
        self.right=None

    def insertLeft(self,value):
        self.left=BTree(value)
        return self.left

    def insertRight(self,value):
        self.right=BTree(value)
        return self.right

    def show(self):
        print self.data

def preorder(node):
    if node.data:
        node.show()
        if node.left:
            preorder(node.left)
        if node.right:
            preorder(node.right)

def inorder(node):
    if node.data:
        if node.left:
            inorder(node.left)
        node.show()
        if node.right:
            inorder(node.right)

def postorder(node):
    if node.data:
        if node.left:
             postorder(node.left)
        if node.right:
            postorder(node.right)
        node.show()
                
if __name__ == "__main__":
    
    Root=BTree("root")
    A=Root.insertLeft("A")
    C=A.insertLeft("C")
    D=C.insertRight("D")
    F=D.insertLeft("F")
    G=D.insertRight("G")
    B=Root.insertRight("B")
    E=B.insertRight("E")

    print "pre-traversal"
    preorder(Root)

    print "in-traversal"
    inorder(Root)

    print "post-traversal"
    postorder(Root)