#!/usr/bin/env python3

 import queue

 class Node(object):

         def __init__(self, data, left=None, right=None):

                 self.data = data

                 self.left = left

                 self.right = right

 tree = Node(1,Node(2,Node(4,Node(8)),Node(5)),Node(3,Node(6),Node(7)))

 def level_traversal(tree):

         q1 = queue.Queue()

         q2 = queue.Queue()

         q1.put(tree)

         try:

                 while not q1.empty() or not q2.empty():

                         while not q1.empty():

                                 e = q1.get()

                                 print(e.data, end=" ")

                                 q2.put(e.left)

                                 q2.put(e.right)

                         print()

                         while not q2.empty():

                                 e = q2.get()

                                 print(e.data, end=" ")

                                 q1.put(e.left)

                                 q1.put(e.right)

                         print()

         except AttributeError:

                 print()

                 print("tree has traversaled")

 if __name__=="__main__":

         level_traversal(tree)