Creating a simple arithmetic expressions tree

[Jona]

So I'm not sure how to write a code that could create a tree placing
data at every node... and then retrieve that information as I go by a
node...
here is what I have
==========CODE===========

from itertools import izip

class Node:
def __init__(self, left, right):
self.left = left
self.right = right

def __str__(self):
return "Node(%s, %s)"%(self.left, self.right)

=========================