Printing BFS (Binary Tree) in Level Order with Specific Formatting

Question

To begin with, this question is not a dup of this one, but builds on it.

Taking the tree in that question as an example,

    1 
   / \\
  2   3
 /            


        

Answer 1

My solution is similar to Alex Martelli's, but I separate traversal of the data structure from processing the data structure. I put the meat of the code into iterLayers to keep printByLayer short and sweet.

from collections import deque

class Node:
    def __init__(self, val, lc=None, rc=None):
        self.val = val
        self.lc = lc
        self.rc = rc

    def iterLayers(self):
        q = deque()
        q.append(self)
        def layerIterator(layerSize):
            for i in xrange(layerSize):
                n = q.popleft()
                if n.lc: q.append(n.lc)
                if n.rc: q.append(n.rc)
                yield n.val
        while (q):
            yield layerIterator(len(q))

    def printByLayer(self):
        for layer in self.iterLayers():
            print ' '.join([str(v) for v in layer])

root = Node(1, Node(2, Node(4, Node(7))), Node(3, Node(5), Node(6)))
root.printByLayer()

which prints the following when run:

1
2 3
4 5 6
7