Object Oriented Programming

Topics / Syllabus

1.         Introduction to Object Oriented Programming 

2.         Difference between object and procedural oriented programming

3.         What are Classes and Objects?

4.         Object-Oriented Programming methodologies:

1. •             Inheritance

2. •             Polymorphism

3. •             Encapsulation

4. •             Abstraction

1.         Introduction to Object Oriented Programming 

Object Oriented Programming is a way of computer programming using the idea of “objects” to represents data and methods. It is also, an approach used for creating neat and reusable code instead of a redundant one.

2.         Difference between object and procedural oriented programming language

Object-Oriented Programming (OOP)

1. It is a bottom-up approach

2. Program is divided into objects

3. Makes use of Access modifiers as ‘public’, private’, protected’

4. It is more secure

5. Object can move freely within member functions

6. It supports inheritance

Procedural-Oriented Programming (POP)

1. It is a top-down approach

2. Program is divided into functions

3. Doesn’t use Access modifiers

4. It is less secure

5. Data can move freely from function to function within programs

6. It does not support inheritance

3.         What are Classes and Objects?

A class is a collection of objects or you can say it is a blueprint of objects defining the common attributes and behavior. Now the question arises, how do you do that?

Class is defined under a “Class” Keyword.

Example: class class1(): // class 1 is the name of the class

Creating an Object and Class in python:

class employee():

def init (self,name,age,id,salary):  //creating a function self.name = name // self is an instance of a class

self.age = age self.salary = salary self.id = id

emp1 = employee("harshit",22,1000,1234) //creating objects

emp2 = employee("arjun",23,2000,2234)

print(emp1. dict )//Prints dictionary

3.  Object-Oriented Programming methodologies:

Inheritance

Polymorphism

Encapsulation

Abstraction 

Inheritance:

Ever heard of this dialogue from relatives “you look exactly like your father/mother” the reason behind this is called ‘inheritance’. From the Programming aspect, It generally means “inheriting or transfer of characteristics from parent to child class without any modification”. The new class is called the derived/child class and the one from which it is derived is called a parent/base class.

Single Inheritance:

Single level inheritance enables a derived class to inherit characteristics from a single parent class.

Example : 

class employee1()://This is a parent class

def init (self, name, age, salary):

self.name = name self.age = age self.salary = salary

class childemployee(employee1)://This is a child class def init       (self, name, age, salary,id):

self.name = name self.age = age self.salary = salary self.id = id

emp1 = employee1('harshit',22,1000) print(emp1.age)

Output ; 22

Multilevel Inheritance:

Multi-level inheritance enables a derived class to inherit properties from an immediate parent class which in turn inherits properties from his parent class.

Example : 

class employee()://Super class

def init (self,name,age,salary): self.name = name

self.age = age self.salary = salary

class childemployee1(employee)://First child class

def init (self,name,age,salary): self.name = name

self.age = age self.salary = salary

class childemployee2(childemployee1)://Second child class

def init (self, name, age, salary):

self.name = name self.age = age self.salary = salary

emp1 = employee('harshit',22,1000)

emp2 = childemployee1('arjun',23,2000)

print(emp1.age) print(emp2.age)

Output ; 22, 23

Hierarchical Inheritance:

Hierarchical level inheritance enables more than one derived class to inherit properties from a parent class. 

Example : 

class employee():

def init (self, name, age, salary): self.name = name  //Hierarchical Inheritance

self.age = age self.salary = salary

class childemployee1(employee):

def init (self,name,age,salary): self.name = name

self.age = age self.salary = salary

class childemployee2(employee):

def init (self, name, age, salary): self.name = name

self.age = age self.salary = salary

emp1 = employee('harshit',22,1000) emp2 = employee('arjun',23,2000)

Multiple Inheritance:

Multiple level inheritance enables one derived class to inherit properties from more than one base class.

Example:

class employee1(): //Parent class

def   init (self, name, age, salary): self.name = name

self.age = age self.salary = salary

class employee2(): //Parent class

def init (self,name,age,salary,id):

self.name = name self.age = age self.salary = salary self.id = id

class childemployee(employee1,employee2): def init  (self, name, age, salary,id): self.name = name

self.age = age self.salary = salary self.id = id

emp1 = employee1('harshit',22,1000) emp2 = employee2('arjun',23,2000,1234)

Polymorphism:

You all must have used GPS for navigating the route, Isn’t it amazing how many different routes you come across for the same destination depending on the traffic, from a programming point of view this is called ‘polymorphism’. It is one such OOP methodology where one task can be performed in several different ways. To put it in simple words, it is a property of an object which allows it to take multiple forms.

Polymorphism is of two types:

• Compile-time Polymorphism

• Run-time Polymorphism

Compile-time Polymorphism:

A compile-time polymorphism also called as static polymorphism which gets resolved during the compilation time of the program. One common example is “method overloading”

class employee1(): def name(self):

print("Harshit is his name")

def salary(self):

print("3000 is his salary") def age(self):

print("22 is his age")

class employee2():

def name(self):

print("Rahul is his name") def salary(self):

print("4000 is his salary")

def age(self):

print("23 is his age")

def func(obj)://Method Overloading obj.name()

obj.salary() obj.age()

obj_emp1 = employee1() obj_emp2 = employee2() func(obj_emp1) func(obj_emp2)

Output:

Harshit is his name 3000 is his salary 22 is his age

Rahul is his name 4000 is his salary

23 is his age

Run-time Polymorphism:

A run-time Polymorphism is also, called as dynamic polymorphism where it gets resolved into the run time. One common example of Run-time polymorphism is “method overriding”.

Example : 

class employee():

def init (self,name,age,id,salary): 

self.name = name

self.age = age 

self.salary = salary 

self.id = id

def earn (self): pass

class childemployee1(employee):

def earn(self): //Run-time polymorphism print("no money")

class childemployee2(employee): def earn(self):

print("has money")

c = childemployee1

c.earn(employee)

d = childemployee2 d.earn(employee)

Output: no money, has money

Abstraction:

Suppose you booked a movie ticket from bookmyshow using net banking or any other process. You don’t know the procedure of how the pin is generated or how the verification is done. This is called ‘abstraction’ from the programming aspect, it basically means you only show the implementation details of a particular process and hide the details from the user.