Recap: Template Method Pattern

The base class owns the order, and subclasses own the steps.

Template Method writes an algorithm's order once, in a base class, and leaves the varying steps to subclasses.

Intent. Define the skeleton of an algorithm in one method, deferring some steps to subclasses.
Three kinds of method. The template method, which subclasses must not override; abstract steps, which they must write; hooks, which they may override.
Direction of control. The base class calls the subclass, the Hollywood principle.
In the wild. unittest.TestCase.run, which calls setUp, the test and tearDown.
In Python. Pass the varying steps as functions when there are few and they share no state.
The trap. A subclass that overrides the template method and skips a step; Java's final stops it, and in Python a type checker reads typing.final.
When not. Steps chosen at run time, or subclasses that would override most of the skeleton.

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