ClassesandObjects.md

Classes and Objects

Basic of class and Objects

What is mean by class

• Almost everything in Python is an object, with its properties and methods.
• The primitive data structures available in Python, like numbers, strings, and lists are designed to represent simple things. But when you need to handle complex things we required classes.
• Classes are used to create new user-defined data structures that contain arbitrary information about something. 

Consider a simple example if there are 5 people and you want to save age, name, salary normally then you need to creates lots of variables for each person.you can reduce this using classes and objects. Just normal create a class with age, name, salary attribute And create a class object for every person when you calling to class.

• a class just provides structure—it’s a blueprint for how something should be defined.
• A class is a code template for creating objects. Objects have member variables and have behavior associated with them.
• the class contains a collection of attributes and methods.

How to define a class in Python?

• In Python, a class is created using class keyword
• Then you add the name of the class (starting with a capital letter.)

Syntax:

class <class name>:
        #attributes
        #methods

#Or another way 
class <class name>():
        #attributes
        #methods

Example:

class Person:
     #initialize the variable(attributes)
     name="python"

    #initialize the methods(functions)
     def Display(self):
            print("i am from Display method")

Another Example:-

class Person():
     #initialize the variable(attributes)
     name="python"

    #initialize the methods(functions)
     def Display(self):
            print("i am from Display method")

Note:-if you run above program you will not get any output because a class is useless until it's an object is created.

How to create an empty class

Example:

class Person:
       pass

Some standard rules to create a class

• class name first character should be in a capital case.
• The class name must be started with alphabets and underscore(_).
• Do not use special keywords as the class name.
• do not use a special character in the class name except underscore(_).
• the class name can be a combination of alphabets, digit, underscore but the starting character should be underscore or alphabets only.
• do not use space in the class name.

Objects

what is mean by object

• An object is an instance of a class.
• Using an object we can access class attributes and methods.
• we can also modify public class attributes using the object.

How to create a class object

After defining the class the procedure to create an object of a class

• use the class name to create an object

Syntax:

#Without parameter
objectname=classname()

#With Parameter
objectname=classname(parameter list)

Example:

#initilize the class
class Person:
   #initialize the variable(attributes)
     name="python"

    #initialize the methods(functions)
     def Display(self):
            print("i am from Display method")

#initialize the class objects
p1=Person()

#create another class object
p2=Person()

#create third class object
p3=Person()