Class and Objects

Python is an object oriented programming language. Unlike procedure oriented programming, where 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. And, class is a blueprint for the object. We can think of class as 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

Create Class in Python

class MyClass:

    x=5

Create an Object

obj=MyClass()

print(p1.x)

The __init__() Function
The examples above are classes and objects in their simplest form, and are not really useful in real life applications. To understand the meaning of classes we have to understand the built-in __init__() function. All classes have a function called __init__(), which is always executed when the class is being initiated.Use the __init__() function to assign values to object properties, or other operations that are necessary to do when the object is being created:

Create a class named Person,use the __init__() function to assign values for name and age:

class Person:
  def __init__(self, name, age):
    self.name = name
    self.age = age

p1 = Person("John", 36)
print(p1.name)
print(p1.age)

Note: The __init__() function is called automatically every time the class is being used to create a new object.

Object Methods

Objects can also contain methods. Methods in objects are functions that belong to the object.

Let us create a method in the Person class:

Insert a function that prints a greeting, and execute it on the p1 object:
class Person:
  def __init__(self, name, age):
    self.name = name
    self.age = age

  def myfunc(self):
    print("Hello my name is " + self.name)

p1 = Person("John", 36)
p1.myfunc()

Note: The self parameter is a reference to the current instance of the class, and is used to access variables that belong to the class.

The self Parameter

The self parameter is a reference to the current instance of the class, and is used to access variables that belongs to the class.It does not have to be named self , you can call it whatever you like, but it has to be the first parameter of any function in the class:

Use the words mysillyobject and abc instead of self:
class Person:
  def __init__(mysillyobject, name, age):
    mysillyobject.name = name
    mysillyobject.age = age

  def myfunc(abc):
    print("Hello my name is " + abc.name)

p1 = Person("John", 36)
p1.myfunc()