What special method is automatically executed when a class is instantiated?

__init__() is the constructor method that is automatically executed when creating a class instance, used to initialize attributes. Unlike __new__() (which actually creates the instance and is rarely overwritten), __init__() receives the already created instance (self) and sets its initial state. It should not return any value except None. It is one of the many special or 'dunder' (double underscore) methods in Python.