Python Design Patterns¶ Welcome! I’m Brandon Rhodes (website, Twitter) and this is my evolving guide to design patterns in the Python programming language. This site is letting me collect …

Let’s take a single design problem and watch how this principle works itself out through several of the classic Gang of Four design patterns. Each design pattern will assemble simple classes, …

The Global Object Pattern¶ In the full-fledged Global Object pattern, as in the Constant pattern, a module instantiates an object at import time and assigns it a name in the module’s global …

The Sentinel Object pattern is a standard Pythonic approach that’s used both in the Standard Library and beyond. The pattern most often uses Python’s built-in None object, but in …

How can a class implement the Iterator Pattern and plug in to Python’s native iteration mechanisms for, iter(), and next()? The container must offer an __iter__() method that returns …

The design pattern became famous as the “Decorator Pattern” with the 1994 publication of the Gang of Four’s Design Patterns book. In 2003, the Python core developers decided to re-use …

This site examines the old patterns from the Gang of Four in the context of a modern dynamic programming language in which classes and functions are first-class objects, to see which …

Python programmers almost never implement the Singleton Pattern as described in the Gang of Four book, whose Singleton class forbids normal instantiation and instead offers a class …

The full-fledged Builder Pattern as imagined by the Gang of Four arranged for a single series of method calls to power the creation of several different object hierarchies — but that use of the …

If the costs and benefits strike a similar balance for a module of your own you are designing, then the Prebound Method pattern can let you deliver remarkable convenience. The pattern¶ To …