avl tree implementation

avl.py

class Node:
    def __init__(self, num):
        self.data   = num
        self.left   = None
        self.right  = None

root = None

def add_to_tree(element, root):
    if root == None:
        root = Node(element)
    elif element > root.data:
        root.right  = add_to_tree(element, root.right)
    elif element < root.data:
        root.left   = add_to_tree(element, root.left)
    return root

def treeprint(root, indent=0):
    if root:
        treeprint(root.left, indent + 1)
        print(" " * indent, root.data)
        treeprint(root.right, indent + 1)

while True:
    try:
        c = input()
    except EOFError as EOF:
        break
    root = add_to_tree(int(c), root)

treeprint(root)