Got asked about a Binary Search Tree so this is my lazy implementation

bst.py

#!/usr/bin/env python

class BST():
    value = None
    left = None
    right = None
    
    def __init__(self, value=None):
        self.value = value
        
    def insert(self, value):
        if self.value == None:
            self.value = value
            return
        if value > self.value:
            if self.right:
                self.right.insert(value)
            else:
                self.right = BST(value)
        elif value < self.value:
            if self.left:
                self.left.insert(value)
            else:
                self.left = BST(value)
                
    def show(self):
        myStr = str(self.value)
        if self.left:
            myStr += "[" + self.left.show() +"]"
        if self.right:
            myStr += "[" + self.right.show() +"]"
        return myStr
        
foo = BST()
foo.insert(10)
foo.insert(20)
foo.insert(5)
foo.insert(15)
foo.insert(30)
print foo.show()