Python's sorted() and list.sort() functions are examples of the Strategy pattern. Both functions accept a named parameter key, which is basically the name of the function that implements a sorting Strategy [Eckel08, page 202].
The following example (the code is in the langs.py file) shows how two different strategies can be used to sort programming languages in the following ways:
Alphabetically
Based on their popularity (using the TIOBE index [j.mp/tiobe14])
A namedtuple programming language [j.mp/namedtuple] is used to keep the statistics of the programming languages. A named tuple is an easy-to-create, lightweight, immutable object type. It is compatible with a normal tuple but it can also be treated as an object (can be called by name, using the usual class notation). A named tuple can be used [j.mp/sonamed]:
Instead of a class when we want to focus on immutability
Instead of a tuple, when it makes sense to use the object notation to create more readable code
I took the liberty...