Object Oriented Programming in Python: Glossary

Anything that we can store in a variable in Python is an object

Every object in Python has a class (or type)

list and numpy.ndarray are commonly-used classes; lists and arrays are corresponding objects

Calling the class as a function constructs new objects of that class

Classes can inherit from other classes; objects of the subclass are automatically also of the parent class

Classes in Python are blocks started with the class keyword

Method definitions look like functions, but must take a self argument

The __init__ method is called when instances are constructed

Adding a class in parentheses after a class definition indicates that the new class is a subclass of the bracketed class (parent class).

The subclass inherits all of that parent class’s attributes and methods.

Defining a method with the same name as one of the parent class’s overrides it.

Use super() to access parent classes and their methods.

A decorator adds functionality to a class or function. To use the decoratorname decorator, add @decoratorname one line before the class or function definition.

Use the @classmethod decorator to indicate methods to be called from the class rather than from an instance.

Use the @property decorator to control access to instance variables

Implement methods like __eq__, __add__, and __gt__ to allow operations such as arithmetic and comparisons.

Implement __repr__ to get more meaningful printouts when you output an object.

Implement methods like __len__, __iter__, and __reversed__ to make instances of a class behave like a collection or iterable.

Implement the __call__ method to make instances of a class callable like functions.

Provided a class exposes all required functionality for an operation to work, Python allows it.

Only use inheritance to express relationships where the subclass is the same kind of thing as the superclass.

Implementing interfaces and adding functionality with composition can be better alternatives to inheritance in some cases.