Pythonisms

Enriching Your Python Classes With Dunder (Magic, Special) Methods

What Are Dunder Methods

In Python, special methods are a set of predefined methods you can use to enrich your classes. They are easy to recognize because they start and end with double underscores, for example __init__ or __str__.

examples

1. you can add a __len__ dunder method to your class to make it return something with len()

2. You can implement a __getitem__ method which allows you to use Python’s list slicing syntax: obj[start:stop].

Object Representation: str, repr

It’s common practice in Python to provide a string representation of your object for the consumer of your class (a bit like API documentation.) There are two ways to do this using dunder methods:

• __repr__: The “official” string representation of an object. This is how you would make an object of the class. The goal of __repr__ is to be unambiguous.

• __str__: The “informal” or nicely printable string representation of an object. This is for the enduser.

Python Iterators

Objects that support the __iter__ and __next__ dunder methods automatically work with for-in loops.