Summary

This chapter covered the decorator pattern and its relationship to the Python programming language. We use the decorator pattern as a convenient way of extending the behavior of an object without using inheritance. Python, with its built-in decorator feature, extends the decorator concept even more, by allowing us to extend the behavior of any callable (function, method, or class) without using inheritance or composition.

We have seen a few examples of real-world objects that are decorated, such as cameras. From a software point of view, both Django and Pyramid use decorators to achieve different goals, such as controlling HTTP compression and caching.

The decorator pattern is a great solution for implementing cross-cutting concerns because they are generic and do not fit well into the OOP paradigm. We mentioned several categories of cross-cutting concerns in the Use cases section. In fact, in the Implementation section, a cross-cutting concern was demonstrated: memoization. We saw...