Adds description to Abstract Factory

Author: lucasloisp

creational/abstract_factory.py

@@ -1,9 +1,34 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-# http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/
+"""
+*What is this pattern about?
+The Abstract Factory Pattern serves to provide an interface for
+creating related/dependent objects without need to specify their
+actual class.
+The idea is to abstract the creation of objects depending on business
+logic, platform choice, etc.
+
+*What does this example do?
+This particular implementation abstracts the creation of a pet and
+does so depending on the AnimalFactory we chose (Dog or Cat)
+This works because both Dog/Cat and their factories respect a common
+interface (.speak(), get_pet() and get_food()).
+Now my application can create pets (and feed them) abstractly and decide later,
+based on my own criteria, dogs over cats.
+The second example allows us to create pets based on the string passed by the
+user, using cls.__subclasses__ (the list of sub classes for class cls)
+and sub_cls.__name__ to get its name.
+
+*Where is the pattern used practically?
+
+*References:
+https://sourcemaking.com/design_patterns/abstract_factory
+http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/
+
+"""
+
 
-"""Implementation of the abstract factory pattern"""
 import six
 import abc
 import random