Print a binary tree of integers in level order.

tree_level_order.py

#!/usr/bin/python

class Node:

    def __init__(self, value, children=[]):
        self.children = children
        self.value = value

    def tree_level_order(self):
        level = [self]
        while level:
            print ' '.join([str(node.value) for node in level])
            level = [child for node in level for child in node.children]

tree = Node(1, \
        [Node(2, [Node(4)]),\
        Node(3, [Node(5), Node(6)])])

tree.tree_level_order()