Binary Search Tree

class binaryTreeNode():
    def __init__(self,data=None):
        self.data = data
        self.left = None
        self.right = None
    def printBinaryTree(self,s = '---'):
        if self.data:
            print(s+self.data)
            s = '   ' + s
            if self.left:
                self.left.printBinaryTree(s)
            if self.right:
                self.right.printBinaryTree(s)
    def insertWord(self,word):
        v = self
        while v.data:
            if word < v.data:
                if v.left:
                    v = v.left
                else:
                    v.left = binaryTreeNode()
                    v = v.left
            else:
                if v.right:
                    v = v.right
                else:
                    v.right = binaryTreeNode()
                    v = v.right
        v.data = word
        return self

wordList = ['mathematics','physics','geography',
            'zoology','meteorology','geology',
            'psychology','chemistry']

tree = binaryTreeNode()

for word in wordList:
    tree.insertWord(word)

tree.printBinaryTree()