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Menu iconMenu iconPython Programming Unlocked for Beginners
Python Programming Unlocked for Beginners
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Chapter 8: Object-Oriented Programming
8.1 Classes and Objects
8.2: Attributes and Methods
8.3: Inheritance
8.4: Polymorphism
8.5: Encapsulation
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Chapter 8: Object-Oriented Programming

8.1 Classes and Objects

Welcome to Chapter 8! In this chapter, we'll dive into the world of Object-Oriented Programming (OOP). OOP is a programming paradigm that allows you to create reusable, modular code by modeling real-world entities as software objects.

Python is an ideal language for OOP, as it fully supports OOP concepts and has a wide range of libraries and frameworks available for implementing OOP. By learning OOP in Python, you'll gain a deeper understanding of programming concepts and be able to create more efficient and effective code. 

Additionally, OOP is a widely used programming paradigm in many industries, including software development, artificial intelligence, and web development. By mastering OOP in Python, you'll be setting yourself up for success in a variety of programming fields. 

In object-oriented programming, the main concepts are classes and objects. A class is a blueprint for creating objects, which are instances of the class. Classes define the properties (attributes) and behavior (methods) of the objects they represent. 

Let's start with a simple example. Consider a class named Dog. The Dog class can have attributes like name, breed, and age. It can also have methods like bark() and sit().

To define a class in Python, you use the class keyword:

class Dog:
    pass

The pass keyword is a placeholder that does nothing, but it allows the class definition to be syntactically correct.

Now that we have our Dog class, we can create objects (instances) of the class:

dog1 = Dog()
dog2 = Dog() 

Here, dog1 and dog2 are two different objects of the Dog class. They are separate instances, so we can assign different attributes to them:

dog1.name = "Buddy"
dog1.breed = "Golden Retriever"
dog1.age = 3

dog2.name = "Max"
dog2.breed = "Labrador"
dog2.age = 5

Now, let's add some methods to our Dog class:

class Dog:
    def bark(self):
        print("Woof!")

    def sit(self):
        print(f"{self.name} sits.")

The self parameter in the method definition is a reference to the instance of the class. It allows you to access the object's attributes and call other methods within the class.

Now, we can create instances of our updated Dog class and call their methods:

dog1 = Dog()
dog1.name = "Buddy"
dog1.bark()  # Output: Woof!
dog1.sit()   # Output: Buddy sits.

dog2 = Dog()
dog2.name = "Max"
dog2.bark()  # Output: Woof!
dog2.sit()   # Output: Max sits.

In this section, we have learned the basics of defining classes and creating objects in Python. However, it is important to note that there are many different types of classes that can be defined, each with their own unique characteristics and behaviors. 

For example, some classes may require additional parameters to be defined in their constructors, while others may inherit properties and methods from parent classes. Additionally, the concept of encapsulation is a fundamental aspect of object-oriented programming, which involves restricting access to certain properties and methods within a class in order to maintain data integrity and prevent unintended modifications.

As we move forward in this book, we will explore these more advanced OOP concepts in greater detail, building upon the foundation that we have established in this section.

Exercise 8.1.1: Define a Car class

In this exercise, you will define a Car class with two attributes make and model, and a method honk() that prints "Beep! Beep!".

Instructions:

  1. Define a Car class with attributes make and model.
  2. Add a honk() method to the Car class that prints "Beep! Beep!".
  3. Create an instance of the Car class, set its make and model attributes, and call its honk() method.

Solution:

class Car:
    def honk(self):
        print("Beep! Beep!")

my_car = Car()
my_car.make = "Toyota"
my_car.model = "Corolla"
my_car.honk()  # Output: Beep! Beep!

Exercise 8.1.2: Define a Circle class

In this exercise, you will define a Circle class with an attribute radius and two methods area() and circumference() that calculate and return the area and circumference of the circle, respectively.

Instructions:

  1. Define a Circle class with an attribute radius.
  2. Add an area() method that calculates and returns the area of the circle using the formula area = pi * radius^2. You can use math.pi for the value of pi.
  3. Add a circumference() method that calculates and returns the circumference of the circle using the formula circumference = 2 * pi * radius.
  4. Create an instance of the Circle class, set its radius attribute, and call its area() and circumference() methods.

Solution:

import math

class Circle:
    def area(self):
        return math.pi * self.radius ** 2

    def circumference(self):
        return 2 * math.pi * self.radius

my_circle = Circle()
my_circle.radius = 5
print(my_circle.area())         # Output: 78.53981633974483
print(my_circle.circumference())  # Output: 31.41592653589793

Exercise 8.1.3: Define a BankAccount class

In this exercise, you will define a BankAccount class with two attributes account_number and balance, and two methods deposit(amount) and withdraw(amount) for depositing and withdrawing money.

Instructions:

  1. Define a BankAccount class with attributes account_number and balance.
  2. Add a deposit(amount) method that increases the balance by the given amount.
  3. Add a withdraw(amount) method that decreases the balance by the given amount, but only if there's enough balance to cover the withdrawal.
  4. Create an instance of the BankAccount class, set its account_number and balance attributes, and call its deposit() and withdraw() methods.

Solution:

class BankAccount:
    def deposit(self, amount):
        self.balance += amount

    def withdraw(self, amount):
        if amount <= self.balance:
            self.balance -= amount
        else:
            print("Insufficient balance")

my_account = BankAccount()
my_account.account_number = "123456789"
my_account.balance = 500
my_account.deposit(300)
print(my_account.balance)  # Output: 800
my_account.withdraw(200)
print(my_account.balance)  # Output: 600
my_account.withdraw(800)   # Output: Insufficient balance
``

8.1 Classes and Objects

Welcome to Chapter 8! In this chapter, we'll dive into the world of Object-Oriented Programming (OOP). OOP is a programming paradigm that allows you to create reusable, modular code by modeling real-world entities as software objects.

Python is an ideal language for OOP, as it fully supports OOP concepts and has a wide range of libraries and frameworks available for implementing OOP. By learning OOP in Python, you'll gain a deeper understanding of programming concepts and be able to create more efficient and effective code. 

Additionally, OOP is a widely used programming paradigm in many industries, including software development, artificial intelligence, and web development. By mastering OOP in Python, you'll be setting yourself up for success in a variety of programming fields. 

In object-oriented programming, the main concepts are classes and objects. A class is a blueprint for creating objects, which are instances of the class. Classes define the properties (attributes) and behavior (methods) of the objects they represent. 

Let's start with a simple example. Consider a class named Dog. The Dog class can have attributes like name, breed, and age. It can also have methods like bark() and sit().

To define a class in Python, you use the class keyword:

class Dog:
    pass

The pass keyword is a placeholder that does nothing, but it allows the class definition to be syntactically correct.

Now that we have our Dog class, we can create objects (instances) of the class:

dog1 = Dog()
dog2 = Dog() 

Here, dog1 and dog2 are two different objects of the Dog class. They are separate instances, so we can assign different attributes to them:

dog1.name = "Buddy"
dog1.breed = "Golden Retriever"
dog1.age = 3

dog2.name = "Max"
dog2.breed = "Labrador"
dog2.age = 5

Now, let's add some methods to our Dog class:

class Dog:
    def bark(self):
        print("Woof!")

    def sit(self):
        print(f"{self.name} sits.")

The self parameter in the method definition is a reference to the instance of the class. It allows you to access the object's attributes and call other methods within the class.

Now, we can create instances of our updated Dog class and call their methods:

dog1 = Dog()
dog1.name = "Buddy"
dog1.bark()  # Output: Woof!
dog1.sit()   # Output: Buddy sits.

dog2 = Dog()
dog2.name = "Max"
dog2.bark()  # Output: Woof!
dog2.sit()   # Output: Max sits.

In this section, we have learned the basics of defining classes and creating objects in Python. However, it is important to note that there are many different types of classes that can be defined, each with their own unique characteristics and behaviors. 

For example, some classes may require additional parameters to be defined in their constructors, while others may inherit properties and methods from parent classes. Additionally, the concept of encapsulation is a fundamental aspect of object-oriented programming, which involves restricting access to certain properties and methods within a class in order to maintain data integrity and prevent unintended modifications.

As we move forward in this book, we will explore these more advanced OOP concepts in greater detail, building upon the foundation that we have established in this section.

Exercise 8.1.1: Define a Car class

In this exercise, you will define a Car class with two attributes make and model, and a method honk() that prints "Beep! Beep!".

Instructions:

  1. Define a Car class with attributes make and model.
  2. Add a honk() method to the Car class that prints "Beep! Beep!".
  3. Create an instance of the Car class, set its make and model attributes, and call its honk() method.

Solution:

class Car:
    def honk(self):
        print("Beep! Beep!")

my_car = Car()
my_car.make = "Toyota"
my_car.model = "Corolla"
my_car.honk()  # Output: Beep! Beep!

Exercise 8.1.2: Define a Circle class

In this exercise, you will define a Circle class with an attribute radius and two methods area() and circumference() that calculate and return the area and circumference of the circle, respectively.

Instructions:

  1. Define a Circle class with an attribute radius.
  2. Add an area() method that calculates and returns the area of the circle using the formula area = pi * radius^2. You can use math.pi for the value of pi.
  3. Add a circumference() method that calculates and returns the circumference of the circle using the formula circumference = 2 * pi * radius.
  4. Create an instance of the Circle class, set its radius attribute, and call its area() and circumference() methods.

Solution:

import math

class Circle:
    def area(self):
        return math.pi * self.radius ** 2

    def circumference(self):
        return 2 * math.pi * self.radius

my_circle = Circle()
my_circle.radius = 5
print(my_circle.area())         # Output: 78.53981633974483
print(my_circle.circumference())  # Output: 31.41592653589793

Exercise 8.1.3: Define a BankAccount class

In this exercise, you will define a BankAccount class with two attributes account_number and balance, and two methods deposit(amount) and withdraw(amount) for depositing and withdrawing money.

Instructions:

  1. Define a BankAccount class with attributes account_number and balance.
  2. Add a deposit(amount) method that increases the balance by the given amount.
  3. Add a withdraw(amount) method that decreases the balance by the given amount, but only if there's enough balance to cover the withdrawal.
  4. Create an instance of the BankAccount class, set its account_number and balance attributes, and call its deposit() and withdraw() methods.

Solution:

class BankAccount:
    def deposit(self, amount):
        self.balance += amount

    def withdraw(self, amount):
        if amount <= self.balance:
            self.balance -= amount
        else:
            print("Insufficient balance")

my_account = BankAccount()
my_account.account_number = "123456789"
my_account.balance = 500
my_account.deposit(300)
print(my_account.balance)  # Output: 800
my_account.withdraw(200)
print(my_account.balance)  # Output: 600
my_account.withdraw(800)   # Output: Insufficient balance
``

8.1 Classes and Objects

Welcome to Chapter 8! In this chapter, we'll dive into the world of Object-Oriented Programming (OOP). OOP is a programming paradigm that allows you to create reusable, modular code by modeling real-world entities as software objects.

Python is an ideal language for OOP, as it fully supports OOP concepts and has a wide range of libraries and frameworks available for implementing OOP. By learning OOP in Python, you'll gain a deeper understanding of programming concepts and be able to create more efficient and effective code. 

Additionally, OOP is a widely used programming paradigm in many industries, including software development, artificial intelligence, and web development. By mastering OOP in Python, you'll be setting yourself up for success in a variety of programming fields. 

In object-oriented programming, the main concepts are classes and objects. A class is a blueprint for creating objects, which are instances of the class. Classes define the properties (attributes) and behavior (methods) of the objects they represent. 

Let's start with a simple example. Consider a class named Dog. The Dog class can have attributes like name, breed, and age. It can also have methods like bark() and sit().

To define a class in Python, you use the class keyword:

class Dog:
    pass

The pass keyword is a placeholder that does nothing, but it allows the class definition to be syntactically correct.

Now that we have our Dog class, we can create objects (instances) of the class:

dog1 = Dog()
dog2 = Dog() 

Here, dog1 and dog2 are two different objects of the Dog class. They are separate instances, so we can assign different attributes to them:

dog1.name = "Buddy"
dog1.breed = "Golden Retriever"
dog1.age = 3

dog2.name = "Max"
dog2.breed = "Labrador"
dog2.age = 5

Now, let's add some methods to our Dog class:

class Dog:
    def bark(self):
        print("Woof!")

    def sit(self):
        print(f"{self.name} sits.")

The self parameter in the method definition is a reference to the instance of the class. It allows you to access the object's attributes and call other methods within the class.

Now, we can create instances of our updated Dog class and call their methods:

dog1 = Dog()
dog1.name = "Buddy"
dog1.bark()  # Output: Woof!
dog1.sit()   # Output: Buddy sits.

dog2 = Dog()
dog2.name = "Max"
dog2.bark()  # Output: Woof!
dog2.sit()   # Output: Max sits.

In this section, we have learned the basics of defining classes and creating objects in Python. However, it is important to note that there are many different types of classes that can be defined, each with their own unique characteristics and behaviors. 

For example, some classes may require additional parameters to be defined in their constructors, while others may inherit properties and methods from parent classes. Additionally, the concept of encapsulation is a fundamental aspect of object-oriented programming, which involves restricting access to certain properties and methods within a class in order to maintain data integrity and prevent unintended modifications.

As we move forward in this book, we will explore these more advanced OOP concepts in greater detail, building upon the foundation that we have established in this section.

Exercise 8.1.1: Define a Car class

In this exercise, you will define a Car class with two attributes make and model, and a method honk() that prints "Beep! Beep!".

Instructions:

  1. Define a Car class with attributes make and model.
  2. Add a honk() method to the Car class that prints "Beep! Beep!".
  3. Create an instance of the Car class, set its make and model attributes, and call its honk() method.

Solution:

class Car:
    def honk(self):
        print("Beep! Beep!")

my_car = Car()
my_car.make = "Toyota"
my_car.model = "Corolla"
my_car.honk()  # Output: Beep! Beep!

Exercise 8.1.2: Define a Circle class

In this exercise, you will define a Circle class with an attribute radius and two methods area() and circumference() that calculate and return the area and circumference of the circle, respectively.

Instructions:

  1. Define a Circle class with an attribute radius.
  2. Add an area() method that calculates and returns the area of the circle using the formula area = pi * radius^2. You can use math.pi for the value of pi.
  3. Add a circumference() method that calculates and returns the circumference of the circle using the formula circumference = 2 * pi * radius.
  4. Create an instance of the Circle class, set its radius attribute, and call its area() and circumference() methods.

Solution:

import math

class Circle:
    def area(self):
        return math.pi * self.radius ** 2

    def circumference(self):
        return 2 * math.pi * self.radius

my_circle = Circle()
my_circle.radius = 5
print(my_circle.area())         # Output: 78.53981633974483
print(my_circle.circumference())  # Output: 31.41592653589793

Exercise 8.1.3: Define a BankAccount class

In this exercise, you will define a BankAccount class with two attributes account_number and balance, and two methods deposit(amount) and withdraw(amount) for depositing and withdrawing money.

Instructions:

  1. Define a BankAccount class with attributes account_number and balance.
  2. Add a deposit(amount) method that increases the balance by the given amount.
  3. Add a withdraw(amount) method that decreases the balance by the given amount, but only if there's enough balance to cover the withdrawal.
  4. Create an instance of the BankAccount class, set its account_number and balance attributes, and call its deposit() and withdraw() methods.

Solution:

class BankAccount:
    def deposit(self, amount):
        self.balance += amount

    def withdraw(self, amount):
        if amount <= self.balance:
            self.balance -= amount
        else:
            print("Insufficient balance")

my_account = BankAccount()
my_account.account_number = "123456789"
my_account.balance = 500
my_account.deposit(300)
print(my_account.balance)  # Output: 800
my_account.withdraw(200)
print(my_account.balance)  # Output: 600
my_account.withdraw(800)   # Output: Insufficient balance
``

8.1 Classes and Objects

Welcome to Chapter 8! In this chapter, we'll dive into the world of Object-Oriented Programming (OOP). OOP is a programming paradigm that allows you to create reusable, modular code by modeling real-world entities as software objects.

Python is an ideal language for OOP, as it fully supports OOP concepts and has a wide range of libraries and frameworks available for implementing OOP. By learning OOP in Python, you'll gain a deeper understanding of programming concepts and be able to create more efficient and effective code. 

Additionally, OOP is a widely used programming paradigm in many industries, including software development, artificial intelligence, and web development. By mastering OOP in Python, you'll be setting yourself up for success in a variety of programming fields. 

In object-oriented programming, the main concepts are classes and objects. A class is a blueprint for creating objects, which are instances of the class. Classes define the properties (attributes) and behavior (methods) of the objects they represent. 

Let's start with a simple example. Consider a class named Dog. The Dog class can have attributes like name, breed, and age. It can also have methods like bark() and sit().

To define a class in Python, you use the class keyword:

class Dog:
    pass

The pass keyword is a placeholder that does nothing, but it allows the class definition to be syntactically correct.

Now that we have our Dog class, we can create objects (instances) of the class:

dog1 = Dog()
dog2 = Dog() 

Here, dog1 and dog2 are two different objects of the Dog class. They are separate instances, so we can assign different attributes to them:

dog1.name = "Buddy"
dog1.breed = "Golden Retriever"
dog1.age = 3

dog2.name = "Max"
dog2.breed = "Labrador"
dog2.age = 5

Now, let's add some methods to our Dog class:

class Dog:
    def bark(self):
        print("Woof!")

    def sit(self):
        print(f"{self.name} sits.")

The self parameter in the method definition is a reference to the instance of the class. It allows you to access the object's attributes and call other methods within the class.

Now, we can create instances of our updated Dog class and call their methods:

dog1 = Dog()
dog1.name = "Buddy"
dog1.bark()  # Output: Woof!
dog1.sit()   # Output: Buddy sits.

dog2 = Dog()
dog2.name = "Max"
dog2.bark()  # Output: Woof!
dog2.sit()   # Output: Max sits.

In this section, we have learned the basics of defining classes and creating objects in Python. However, it is important to note that there are many different types of classes that can be defined, each with their own unique characteristics and behaviors. 

For example, some classes may require additional parameters to be defined in their constructors, while others may inherit properties and methods from parent classes. Additionally, the concept of encapsulation is a fundamental aspect of object-oriented programming, which involves restricting access to certain properties and methods within a class in order to maintain data integrity and prevent unintended modifications.

As we move forward in this book, we will explore these more advanced OOP concepts in greater detail, building upon the foundation that we have established in this section.

Exercise 8.1.1: Define a Car class

In this exercise, you will define a Car class with two attributes make and model, and a method honk() that prints "Beep! Beep!".

Instructions:

  1. Define a Car class with attributes make and model.
  2. Add a honk() method to the Car class that prints "Beep! Beep!".
  3. Create an instance of the Car class, set its make and model attributes, and call its honk() method.

Solution:

class Car:
    def honk(self):
        print("Beep! Beep!")

my_car = Car()
my_car.make = "Toyota"
my_car.model = "Corolla"
my_car.honk()  # Output: Beep! Beep!

Exercise 8.1.2: Define a Circle class

In this exercise, you will define a Circle class with an attribute radius and two methods area() and circumference() that calculate and return the area and circumference of the circle, respectively.

Instructions:

  1. Define a Circle class with an attribute radius.
  2. Add an area() method that calculates and returns the area of the circle using the formula area = pi * radius^2. You can use math.pi for the value of pi.
  3. Add a circumference() method that calculates and returns the circumference of the circle using the formula circumference = 2 * pi * radius.
  4. Create an instance of the Circle class, set its radius attribute, and call its area() and circumference() methods.

Solution:

import math

class Circle:
    def area(self):
        return math.pi * self.radius ** 2

    def circumference(self):
        return 2 * math.pi * self.radius

my_circle = Circle()
my_circle.radius = 5
print(my_circle.area())         # Output: 78.53981633974483
print(my_circle.circumference())  # Output: 31.41592653589793

Exercise 8.1.3: Define a BankAccount class

In this exercise, you will define a BankAccount class with two attributes account_number and balance, and two methods deposit(amount) and withdraw(amount) for depositing and withdrawing money.

Instructions:

  1. Define a BankAccount class with attributes account_number and balance.
  2. Add a deposit(amount) method that increases the balance by the given amount.
  3. Add a withdraw(amount) method that decreases the balance by the given amount, but only if there's enough balance to cover the withdrawal.
  4. Create an instance of the BankAccount class, set its account_number and balance attributes, and call its deposit() and withdraw() methods.

Solution:

class BankAccount:
    def deposit(self, amount):
        self.balance += amount

    def withdraw(self, amount):
        if amount <= self.balance:
            self.balance -= amount
        else:
            print("Insufficient balance")

my_account = BankAccount()
my_account.account_number = "123456789"
my_account.balance = 500
my_account.deposit(300)
print(my_account.balance)  # Output: 800
my_account.withdraw(200)
print(my_account.balance)  # Output: 600
my_account.withdraw(800)   # Output: Insufficient balance
``
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