(10)_python-class-and-object.py

# Python Class and Object
# ========================
# Adapted From: Programiz
# Tutorial Title: Python Class and Object
# URL: https://www.programiz.com/python-programming

# Python is a versatile programming language that supports various programming styles,
# including object-oriented programming (OOP) through the use of classes and objects.

# (1) Python Classes
# We use the class keyword to create a class in Python. For example,
class Bike:
    name = ""
    gear = 0

# (2) Python Objects
# An object is called an instance of a class. For example, suppose Bike is a class then we can create objects like bike1, bike2, etc. from the class.
# Here's the syntax to create an object.
# create class
class Bike:
    name = ""
    gear = 0
# create objects of class
bike1 = Bike()
bike2 = Bike()

# (3) Access Class Attributes Using Objects
# We use the . notation to access the attributes of a class. For example,
# define a class
class Bike:
    name = ""
    gear = 0
# create object of class
bike1 = Bike()
# access attributes and assign new values
bike1.gear = 11
bike1.name = "Mountain Bike"
print(f"Name: {bike1.name}, Gears: {bike1.gear}")

# (4) Create Multiple Objects of Python Class
# define a class
class Employee:
    # define an attribute
    employee_id = 0
# create two objects of the Employee class
employee1 = Employee()
employee2 = Employee()
# access attributes using employee1
employee1.employee_id = 1001
print(f"Employee ID: {employee1.employee_id}")
# access attributes using employee1
employee1.employee_id = 1002
print(f"Employee ID: {employee1.employee_id}")

# (5) Python Methods
# We can also define a function inside a Python class.
# A Python Function defined inside a class is called a method.
# Let's see an example,
# create a class
class Room:
    length = 0.0
    breadth = 0.0
    # method to calculate area
    def calculate_area(self):
        print("Area of Room = ", self.length * self.breadth)
# create object of Room class
study_room = Room()
# assign values to all the attributes
study_room.length = 42.5
study_room.breadth = 30.8
# access method inside class
study_room.calculate_area()

# (6) Python Constructors
#  We can also initialize values using the constructors. For example,
class Bike:
    # constructor function
    def __init__(self, name="", gear=0):
        self.name = name
        self.gear = gear
    def print_bicycle_details(self):
        print(f"Name: {self.name}, Gears: {self.gear}")
# create bicycle objects
bike1 = Bike("Mountain Bike", 11)
bike2 = Bike("City Bike", 6)
# print objects
bike1.print_bicycle_details()
bike2.print_bicycle_details()

# (7) Python Inheritance
# Inheritance is a way of creating a new class for using details of an 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: Use of Inheritance in Python
# base class
class Animal:
    def eat(self):
        print("I can eat!")
    def sleep(self):
        print("I can sleep!")
# derived class
class Dog(Animal):
    def bark(self):
        print("I can bark! Woof woof!!")
# Create object of the Dog class
dog1 = Dog()
# Calling members of the base class
dog1.eat()
dog1.sleep()
# Calling member of the derived class
dog1.bark();

# (8) Python Encapsulation
# Encapsulation is one of the key features of object-oriented programming. Encapsulation refers to the bundling of attributes and methods inside a single class.
# It prevents outer classes from accessing and changing attributes and methods of a class. This also helps to achieve data hiding.
# In Python, we denote private attributes using underscore as the prefix i.e. single _ or double __. For example,
class Computer:
    def __init__(self):
        self.__maxprice = 900
    def sell(self):
        print("Selling Price: {}".format(self.__maxprice))
    def setMaxPrice(self, price):
        self.__maxprice = price
c = Computer()
c.sell()
# change the price
c.__maxprice = 1000
c.sell()
# using setter function
c.setMaxPrice(1050)
c.sell()

# (9) Python Polymorphism
# Polymorphism is another important concept of object-oriented programming. It simply means more than one form.
# That is, the same entity (method or operator or object) can perform different operations in different scenarios.
# Let's see an example,
class Polygon:
    # renders Polygon
    def render(self):
        print("Rendering Polygon ... ")
class Square(Polygon):
    # renders Square
    def render(self):
        print("Rendering Square ... ")
class Circle(Polygon):
    # renders Circle
    def render(self):
        print("Rendering Circle ... ")
# create an object of Square
s1 = Square()
s1.render()

# create an object of Circle
c1 = Circle()
c1.render()