Python classes and objects

Python is an object oriented programming language. Unlike procedure oriented programming, in which the main emphasis is on functions, object oriented programming stress on objects. Object is simply a collection of data (variables) and methods (functions) that act on those data.

Class is a blueprint for the object. We can think of class like a sketch (prototype) of a house. It contains all the details about the floors, doors, windows etc. Based on these descriptions we build the house. House is the object. As, many houses can be made from a description, we can create many objects from a class. An object is also called an instance of a class and the process of creating this object is called instantiation.

Defining a Class in Python

Like function definitions begin with the keyword def, in Python, we define a class using the keyword class. The first string is called docstring and has a brief description about the class. Although not mandatory, this is recommended. Here is a simple class definition.

class MyNewClass:
    '''This is a docstring. I have created a new class'''
    pass

A class creates a new local namespace where all its attributes are defines. Attributes may be data or functions. There are also special attributes in it that begins with double underscores (__). For example, __doc__ gives us the docstring of that class. As soon as we define a class, a new class object is created with the same name. This class object allows us to access the different attributes as well as to instantiate new objects of that class.

>>> class MyClass:
...     "This is my second class"
...     a = 10
...     def func(self):
...         print('Hello')
...   
>>> MyClass.a
10