Dunder Methods

Dunder methods (ie double underscore methods) are methods that are called implicitly by python for instances of a class based on certain scenarios. These methods are not called manually by the programmer though and sometimes feel like magic (hence called magic methods)

One common example of a dunder method that is used often is the __init__ method that is used for initializing an object

                
                    class Square:
                        def __init__(self, side_length):
                            self.side_length = side_length

                    square = Square(1)
                
            

In the above code even though the __init__ method is not called it will be called implicity by python

Operator overloading with Dunder Methods

All python operators actually are implementing the dunder method internally. For example when we have code like value in array_variable, the __contains__ dunder method is actually called

In other words calling value in array_variable is the exact same as value.__contains__(array_variable)

So operator overloading is as easy as just implementing the dunder methods. There are many dunder methods like __str__, __repr__, __new__ etc

Using __repr__ vs __str__

__repr__ and __str__ are two dunder methods that are used to display information about the class to a human. Use __repr__ to print detailed information about a class to the developer / programmer and use __str__ to print basic information about the class to an end user.

Ideally the output of a __repr__ can be directly run in the python repl to create an object