nodes at k python

# http://code2begin.blogspot.com
# Program to print the nodes at distance K from a given node in binary tree
# node class
class node:
    def __init__(self, element):
        self.data = element
        self.left = None
        self.right = None


# function to print child nodes at a distance k from the given node
def print_nodes_at_K(root, K):
    if root is None or K < 0:
        return

    if K == 0:
        print(root.data, end=" ")

    if K > -1:
        print_nodes_at_K(root.left, K - 1)
        print_nodes_at_K(root.right, K - 1)



head = node(1)
head.left = node(2)
head.right = node(3)
head.left.left = node(4)
head.left.right = node(5)
head.right.right = node(6)
head.left.left.right = node(7)
head.right.right.left = node(8)
head.left.left.right.left = node(9)
head.left.left.right.left.left = node(10)
head.right.right.left.right = node(11)
print("Nodes at distance 2 from the root node are : ")
print_nodes_at_K(head, 2)