Recap: Strategy Pattern

The caller picks the algorithm, the context runs it, and in Python it is often a function.

Strategy replaces a conditional that chooses an algorithm with an object, or a function, that the caller hands in.

Intent. Define a family of algorithms, encapsulate each one, and make them interchangeable.
Participants. The strategy interface, one concrete strategy per algorithm, the context that holds one, and the client that chooses it.
The choice. It is made by the caller and can be changed at any time; the context never branches on it.
In the wild. Java's Comparator passed to List.sort, and the function passed as key to Python's sorted.
In Python. A one-method strategy is a function; use a class for a second method or named configuration.
The trap. A context that checks which strategy it holds; move that behaviour into the strategy.
When not. Two fixed options, algorithms that need different inputs, or a choice that follows the object's own state.

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