.. role:: python(code)
   :language: python

.. index::
    oop; iterator
    oop; iterable
    oop; callable
    oop; class attributes

OOP technicalities
------------------

There is much to say about object oriented programming, 
here the focus is only made on few technical points of python objects useful later in the course.

Iterator
^^^^^^^^

An iterator is an object with a :python:`__next__` method. 
It raises an :python:`StopIteration` exception when there is no 'next' item.



Iterable
^^^^^^^^

An iterable is an  object with an :python:`__iter__` method which returns an iterator. 
It is a python object which can be seamlessly iterated over.



Callable
^^^^^^^^

An object can be made callable if a :python:`__call__` method is defined. 
It useful when you need a function with a state.

Class attributes
^^^^^^^^^^^^^^^^

Some attributes can be defined directly under the :python:`class` declaration. 
These attributes are shares between all instances of the class.

.. note::

   Careful! several very popular libraries use some dark magic to automatically define from class attributes 
   the instance attributes for every instance. :python:`dataclass, attrs, django, pydantic` etc. 
   

.. literalinclude:: ../../../../src/tools_methods/basics/oop.py
      :name: OOP
      :linenos:    
      :caption: src