Python Devlopment



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Overview of OOP's

Python is a multi-paradigm programming language. Meaning, it supports different programming approach.

One of the popular approach to solve a programming problem is by creating objects. This is known as Object-Oriented Programming (OOP).

An object has two characteristics:

  • attributes
  • behavior

Let's take an example:

Parrot is an object,

  • name, age, color are the attributes
  • singing, dancing are behavior

The concept of OOP in Python focuses on creating reusable code. This concept is also known as DRY (Don't Repeat Yourself).

In Python, the concept of OOP follows some basic principles:

1. Inheritance : A process of using details from a new class without modifying existing class.

2. Encapsulation : Hiding the private details of a class from other objects.

3. Polymorphism : A concept of using common operation in different ways for different data input.

 

1. Class

A class is a blueprint for the object.

We can think of class as an sketch of a parrot with labels. It contains all the details about the name, colors, size etc. Based on these descriptions, we can study about the parrot. Here, parrot is an object.

The example for class of parrot can be :

class Parrot:
    pass

Here, we use class keyword to define an empty class Parrot. From class, we construct instances. An instance is a specific object created from a particular class.

 

2. Object

An object (instance) is an instantiation of a class. When class is defined, only the description for the object is defined. Therefore, no memory or storage is allocated.

The example for object of parrot class can be:

obj = Parrot()

Here, obj is object of class Parrot.

Suppose we have details of Parrot. Now, we are going to show how to build the class and objects of Human.

Example 1: Creating Class and Object in Python

class Human:

    # class attribute
    species = "bird"

    # instance attribute
    def __init__(self, name, age):
        self.name = name
        self.age = age

# instantiate the Parrot class
blu = Parrot("Blu", 10)
woo = Parrot("Woo", 15)

# access the class attributes
print("Blu is a {}".format(blu.__class__.species))
print("Woo is also a {}".format(woo.__class__.species))

# access the instance attributes
print("{} is {} years old".format( blu.name, blu.age))
print("{} is {} years old".format( woo.name, woo.age))

 

When we run the program, the output will be:

Blu is a bird
Woo is also a bird
Blu is 10 years old
Woo is 15 years old

In the above program, we create a class with name Parrot. Then, we define attributes. The attributes are a characteristic of an object.

 

hen, we create instances of the Parrot class. Here, blu and woo are references (value) to our new objects.

Then, we access the class attribute using __class __.species. Class attributes are same for all instances of a class. Similarly, we access the instance attributes using blu.name and blu.age. However, instance attributes are different for every instance of a class.

 

3. Methods

Methods are functions defined inside the body of a class. They are used to define the behaviors of an object.

Example 2 : Creating Methods in Python

class Parrot:
    
    # instance attributes
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    # instance method
    def sing(self, song):
        return "{} sings {}".format(self.name, song)

    def dance(self):
        return "{} is now dancing".format(self.name)

# instantiate the object
blu = Parrot("Blu", 10)

# call our instance methods
print(blu.sing("'Happy'"))
print(blu.dance())

When we run program, the output will be:

Blu sings 'Happy'
Blu is now dancing

In the above program, we define two methods i.e sing() and dance(). These are called instance method because they are called on an instance object i.e blu.

 

4. Inheritance

Inheritance is a way of creating new class for using details of existing class without modifying it. The newly formed class is a derived class (or child class). Similarly, the existing class is a base class (or parent class).

Example 3: Use of Inheritance in Python

# parent class
class Bird:
    
    def __init__(self):
        print("Bird is ready")

    def whoisThis(self):
        print("Bird")

    def swim(self):
        print("Swim faster")

# child class
class Penguin(Bird):

    def __init__(self):
        # call super() function
        super().__init__()
        print("Penguin is ready")

    def whoisThis(self):
        print("Penguin")

    def run(self):
        print("Run faster")

peggy = Penguin()
peggy.whoisThis()
peggy.swim()
peggy.run()

 

When we run this program, the output will be:

Bird is ready
Penguin is ready
Penguin
Swim faster
Run faster

 

In the above program, we created two classes i.e. Bird (parent class) and Penguin (child class). The child class inherits the functions of parent class. We can see this from swim()method. Again, the child class modified the behavior of parent class. We can see this from whoisThis() method. Furthermore, we extend the functions of parent class, by creating a new run() method.

Additionally, we use super() function before __init__() method. This is because we want to pull the content of __init__() method from the parent class into the child class.