Update heapify.py

heaps/heapify.py

@@ -2,6 +2,13 @@
 # -*- coding: utf-8 -*-
 # author: bt3gl
 
+# python's built-in heap differs from the standard implementation of a heap
+# in two ways. firstly, it uses zero-based indexing, so it stores the root
+# node at index zero instead of the size of the heap. secondly, the built-in
+# module does not offer a direct way to create a max heap, instead, we must
+# modify the values of each eelement when inserting in the heap, and when
+# removing it from the heap.
+
 import heapq
 
 min_heap = [3,1,2]