Differentiation of Python Classes and Objects

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What is Python Classes/Objects?

Python is an object oriented programming language. Almost everything in Python is an object, with its properties and methods. A Class is like an object constructor, or a “blueprint” for creating objects. A class is a user-defined blueprint or prototype from which objects are created. Classes provide a means of bundling data and functionality together. Creating a new class creates a new type of object, allowing new instances of that type to be made. Each class instance can have attributes attached to it for maintaining its state. Class instances can also have methods (defined by their class) for modifying their state.

To understand the need for creating a class let’s consider an example, let’s say you wanted to track the number of dogs that may have different attributes like breed, age. If a list is used, the first element could be the dog’s breed while the second element could represent its age. Let’s suppose there are 100 different dogs, then how would you know which element is supposed to be which? What if you wanted to add other properties to these dogs? This lacks organization and it’s the exact need for classes. 

Class creates a user-defined data structure, which holds its own data members and member functions, which can be accessed and used by creating an instance of that class. A class is like a blueprint for an object.

Some points on Python class:  

  • Classes are created by keyword class.
  • Attributes are the variables that belong to a class.
  • Attributes are always public and can be accessed using the dot (.) operator. Eg.: Myclass.Myattribute

Class Definition Syntax:

 class ClassName:   
 # Statement-1     .     .     . 
 # Statement-N

Defining a class – 

  • Python3
# Python3 program to# demonstrate defining# a class class Dog:pass

In the above example, the class keyword indicates that you are creating a class followed by the name of the class (Dog in this case).

Create a Class

To create a class, use the keyword class:


Create a class named MyClass, with a property named x:

class MyClass:<br>  x = 5

Create Object

An Object is an instance of a Class. A class is like a blueprint while an instance is a copy of the class with actual values. It’s not an idea anymore, it’s an actual dog, like a dog of breed pug who’s seven years old. You can have many dogs to create many different instances, but without the class as a guide, you would be lost, not knowing what information is required.
An object consists of : 

  • State: It is represented by the attributes of an object. It also reflects the properties of an object.
  • Behavior: It is represented by the methods of an object. It also reflects the response of an object to other objects.
  • Identity: It gives a unique name to an object and enables one object to interact with other objects.
python class

Declaring Objects (Also called instantiating a class)

When an object of a class is created, the class is said to be instantiated. All the instances share the attributes and the behavior of the class. But the values of those attributes, i.e. the state are unique for each object. A single class may have any number of instances.


python declaring an object

Declaring an object – 

  • Python3
# Python3 program to# demonstrate instantiating# a class  class Dog: # A simple class# attributeattr1 = "mammal"attr2 = "dog" # A sample method def fun(self):print("I'm a", self.attr1)print("I'm a", self.attr2) # Driver code# Object instantiationRodger = Dog() # Accessing class attributes# and method through objectsprint(Rodger.attr1)Rodger.fun()


I'm a mammal
I'm a dog

In the above example, an object is created which is basically a dog named Rodger. This class only has two class attributes that tell us that Rodger is a dog and a mammal.

Now we can use the class named MyClass to create objects:


Create an object named p1, and print the value of x:

p1 = MyClass()<br>print(p1.x)

The __init__() Function

The __init__ method is the Python equivalent of the C++ constructor in an object-oriented approach. The __init__ function is called every time an object is created from a class. The __init__ method lets the class initialize the object’s attributes and serves no other purpose. It is only used within classes. 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:<br>  def __init__(self, name, age)
:<br>    self.name = name<br>    self.age = age
p1 = Person("John", 36)

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:<br>  def __init__(self, name, age):<br>    self.name = name<br>    self.age = age
  def myfunc(self):
    print("Hello my name is " + self.name)
p1 = Person("John", 36)

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:<br>  def __init__(mysillyobject, name, age):<br>    mysillyobject.name = name<br>    mysillyobject.age = age
  def myfunc(abc):
    print("Hello my name is " + abc.name)
p1 = Person("John", 36)

Modify Object Properties

You can modify properties on objects like this:


Set the age of p1 to 40:

p1.age = 40

Delete Object Properties

You can delete properties on objects by using the del keyword:


Delete the age property from the p1 object:

del p1.age

Delete Objects

You can delete objects by using the del keyword:


Delete the p1 object:

del p1

The pass Statement

class definitions cannot be empty, but if you for some reason have a class definition with no content, put in the pass statement to avoid getting an error.



Differentiation of Python Classes and Objects
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