Add description to the strategy pattern

behavioral/strategy.py

@@ -2,6 +2,24 @@
 # -*- coding: utf-8 -*-
 
 """
+*What is this pattern about?
+This pattern aims to encapsulate each algorithm and allow them to be
+interchangeable. Separating algorithms allows the client to scale
+with larger and more complex algorithms, since the client and the
+strategies are kept independent of each other.
+
+Having the algorithms as an integral part of the client can cause the
+client to be larger and harder to maintain. This is more evident when
+supporting multiple algorithms. The separation of client and algorithm
+allows us to easily replace and vary the algorithm.
+
+*What does this example do?
+Below the 'StrategyExample' is an example of the client while the two
+functions; 'execute_replacement1' and 'execute_replacement2' are
+examples of the implementation or strategy. In the example we can see
+that the client can vary it's 'execute' method by changing the
+strategy which is responsible for implementation.
+
 http://stackoverflow.com/questions/963965/how-is-this-strategy-pattern
  -written-in-python-the-sample-in-wikipedia
 In most of other languages Strategy pattern is implemented via creating some