Python perfect binary tree

perfect_bst.py

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


# Build from last elem first.
# First decrement with right and then left.
def build_tree(height, post):
    if height == 1:
        return Node(post.pop())
    node = Node(post.pop())
    node.right = build_tree(height-1, post)
    node.left = build_tree(height-1, post)
    return node


# A utility function to query tree for node's value and return node's parent
def query_parent(node, num, parent=-1):
    if node == None:
        return
    if (node.value == num):
        return parent
    else:
        ql = query_parent(node.left, num, node.value)
        qr = query_parent(node.right, num, node.value)
        return ql or qr


def solution(h, q):
    post = list(range(1, 2**h))
    tree = build_tree(h, post)
    find_parent = lambda q_val: query_parent(tree, q_val)
    return map(find_parent, q)


print solution(3, [1, 4, 7])  #[3,6,-1]
print solution(3, [7, 3, 5, 1])  #[-1,7,6,3]
print solution(5, [19, 14, 28])  #[21,15,29]