Python Data Model Explained: How Special Methods and Protocols Work

A detailed technical guide explores Python's data model, focusing on special methods — also called magic or dunder methods — and how they enable user-defined classes to integrate with built-in language operations. These methods, such as __len__, __iter__, and __eq__, act as behavioral contracts that tell the Python interpreter which operations a class supports. Rather than relying on type checks, Python uses these protocols to resolve operations like len(), iteration, and arithmetic uniformly across built-in and custom types. The article is based on Python 3.14 documentation and distinguishes between language-level guarantees and CPython-specific implementation details. It serves as Part 2 of a series building on foundational concepts like object identity, mutability, and references introduced earlier.