Stranger Methods

The Python Data Model has more than 80 special method names. Special methods are symbolised with two underscores on either side of a word, for example "__add__". By implementing your own dunder methods Python then calls them when you use them with operators or python's built-ins.

The Python interpreter calls special methods so you do not have to! You do not typically write my_object.__add__, you simple would call + or make another method add that calls the __add__ method you implemented.

Another great example of Python's interpreting calling dunder methods without you know is the __repr__ special method. This is the built-in string representation of the object for inspection. Without a custom __repr__, the Python console would display your class instance as <MyObject object @ 0X11e123476>. The repr built-in is called as a fallback if a __str__ is not created - which is why Python programmers choose to implement __repr__ over __str__ special method. The method can be used with the !r operator when using f-strings or the .format's string method.

Implementing special methods allows our objects to play nice with Python's built-ins and symbol operations. You can inherit an interface by using the Abstract Base Classes (ABCs) defined within the collections.abc module. The ABCs have several abstract method that must be implemented within your sub-class class, otherwise your sub-class class would fail - more on that in another post!