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![Polymorphism Polymorphism with Method Overriding Method Overriding Example Example of polymorphism with method overriding in Python: 1 # Parent class 2 class Animal: 3 def speak(self): 4 return Animal makes a sound 5 6 # Child class overriding speak method 7 class Dog(Animal): 8 def speak(self): 9 return Dog barks 10 11 class Cat(Animal): 12 def speak(self): 13 return Cat meows 14 15 # Polymorphism in action 16 animals = [Animal (), Dog(), Cat()] 17 18 for animal in animals: 19 print(animal.speak ()) # Output depends on the object type Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 32 / 49](https://image.slidesharecdn.com/mainoop-250616105419-39e54bb0/75/Object-oriented-Programming-via-python-pdf-32-2048.jpg)
Object oriented Programming via python.pdf
- 1. Object-Oriented Programming Course: Introductionto Programming and Data Structures Dr. Laltu Sardar Institute for Advancing Intelligence (IAI), TCG Centres for Research and Education in Science and Technology (TCG Crest) Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 1 / 49
- 2. 1 Introduction toObject-Oriented Programming Comparison of Programming Paradigms Classes and Objects Creating and Using Classes 2 Encapsulation What is Encapsulation? Private and Public Members Example of Encapsulation in Python Explanation of Code Why Encapsulation? 3 Inheritance What is Inheritance? Types of Inheritance Example of Single Inheritance Explanation of Code Example of Multilevel Inheritance Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 2 / 49
- 3. Explanation of Code Advantagesof Inheritance 4 Polymorphism What is Polymorphism? Types of Polymorphism Polymorphism with Method Overriding Explanation of Code Polymorphism through Duck Typing Explanation of Duck Typing Code Advantages of Polymorphism 5 Abstraction What is Abstraction? Abstract Classes in Python Example of Abstract Class Explanation of Abstract Class Example Use of Abstraction in Python Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 3 / 49
- 4. Real-World Example ofAbstraction Explanation of Real-World Example Advantages of Abstraction Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 4 / 49
- 5. Introduction to Object-OrientedProgramming Introduction to Object-Oriented Programming Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 5 / 49
- 6. Introduction to Object-OrientedProgramming Comparison of Programming Paradigms Programming Paradigms I Procedural Programming: Focuses on a sequence of instructions or procedures. Functions are the main building blocks. Data and functions are separate; there is no concept of objects. Example: C, Pascal. Object-Oriented Programming (OOP): Organizes code into objects which combine both data (attributes) and behavior (methods). Promotes concepts like inheritance, polymorphism, and encapsulation. Useful for modeling complex systems and relationships between entities. Example: Python, Java, C++. Functional Programming: Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 6 / 49
- 7. Introduction to Object-OrientedProgramming Comparison of Programming Paradigms Programming Paradigms II Treats computation as the evaluation of mathematical functions. Avoids changing-state and mutable data. Emphasizes immutability, higher-order functions, and recursion. Example: Haskell, Lisp, Python (can support functional programming). Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 7 / 49
- 8. Introduction to Object-OrientedProgramming Comparison of Programming Paradigms Key Dierences between the Paradigms I State Management: Procedural: Direct manipulation of state through variables. OOP: State is encapsulated within objects and managed through methods. Functional: Encourages immutability; no direct state manipulation. Code Reuse: Procedural: Functions can be reused, but lacks sophisticated reuse mechanisms. OOP: Code reuse through inheritance and polymorphism. Functional: Code reuse through higher-order functions and pure functions. Modularity: Procedural: Achieved through functions and procedures. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 8 / 49
- 9. Introduction to Object-OrientedProgramming Comparison of Programming Paradigms Key Dierences between the Paradigms II OOP: Achieved through classes and objects. Functional: Achieved through functions and composability. Approach to Problems: Procedural: Focuses on breaking down the problem into sequential steps. OOP: Models problems by dening objects and their interactions. Functional: Focuses on dening mathematical functions to transform data. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 9 / 49
- 10. Introduction to Object-OrientedProgramming Classes and Objects Classes and Objects A Class is a blueprint for creating objects. An Object is an instance of a class. Objects encapsulate both data (attributes) and behavior (methods). Classes promote code reuse through inheritance. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 10 / 49
- 11. Introduction to Object-OrientedProgramming Creating and Using Classes Creating and Using Classes: Example Example of creating and using a class in Python: 1 class Car: 2 def __init__(self , brand , model , year): 3 self.brand = brand 4 self.model = model 5 self.year = year 6 7 def display_info(self): 8 return f'{self.year} {self.brand} {self.model}' 9 10 # Create an object of class Car 11 my_car = Car(Toyota, Corolla, 2020) 12 13 # Using the object 14 print(my_car.display_info ()) Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 11 / 49
- 12. Introduction to Object-OrientedProgramming Creating and Using Classes Explanation of Code The __init__ method is a constructor that initializes the object. self refers to the current instance of the class. The display_info() method returns a formatted string with the car's details. my_car is an instance of the Car class, initialized with brand, model, and year. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 12 / 49
- 13. Encapsulation Encapsulation in Python LaltuSardar (IAI, TCG Crest) Intro to Python Programming 13 / 49
- 14. Encapsulation What isEncapsulation? What is Encapsulation? Encapsulation is one of the core principles of Object-Oriented Programming (OOP). It refers to the bundling of data (attributes) and methods (functions) that operate on the data into a single unit, i.e., a class. Encapsulation also restricts direct access to some of the object's components, which is used to hide the internal representation of the object. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 14 / 49
- 15. Encapsulation Private andPublic Members Private and Public Members In Python, class attributes and methods are by default public. You can make an attribute or method private by prexing it with an underscore (`_` for protected and `__` for private). Private members are not accessible directly outside the class, which ensures that sensitive data is hidden from external access. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 15 / 49
- 16. Encapsulation Example ofEncapsulation in Python Encapsulation: Example I Example of encapsulation in Python: 1 class BankAccount: 2 def __init__(self , owner , balance =0): 3 self.owner = owner 4 self.__balance = balance # Private attribute 5 6 def deposit(self , amount): 7 if amount 0: 8 self.__balance += amount 9 return self.__balance 10 11 def withdraw(self , amount): 12 if 0 amount = self.__balance: 13 self.__balance -= amount 14 return amount 15 else: 16 return Insufficient funds 17 18 def get_balance(self): Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 16 / 49
- 17. Encapsulation Example ofEncapsulation in Python Encapsulation: Example II 19 return self.__balance 20 21 # Create a BankAccount object 22 account = BankAccount(Alice, 1000) 23 24 # Using methods to access private attribute 25 account.deposit (500) 26 print(account.get_balance ()) # Output: 1500 Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 17 / 49
- 18. Encapsulation Explanation ofCode Explanation of Code The attribute __balance is private, meaning it cannot be accessed directly from outside the class. The methods deposit, withdraw, and get_balance are used to modify and access the private attribute __balance. This ensures that the balance cannot be modied directly, only through predened methods, thus ensuring data security. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 18 / 49
- 19. Encapsulation Why Encapsulation? WhyEncapsulation? Encapsulation helps in protecting the internal state of an object. It promotes data integrity by restricting unauthorized or unintended access. Through encapsulation, the object's internal state is only modiable via public methods, providing controlled access. It simplies debugging and helps maintain clean code architecture. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 19 / 49
- 20. Inheritance Inheritance Laltu Sardar (IAI,TCG Crest) Intro to Python Programming 20 / 49
- 21. Inheritance What isInheritance? What is Inheritance? Inheritance is one of the core principles of Object-Oriented Programming (OOP). It allows a class (child class) to inherit attributes and methods from another class (parent class). This promotes code reuse and establishes a relationship between dierent classes. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 21 / 49
- 22. Inheritance Types ofInheritance Types of Inheritance Single Inheritance: A child class inherits from a single parent class. Multiple Inheritance: A child class inherits from multiple parent classes. Multilevel Inheritance: A child class inherits from a parent class, and another class can inherit from the child class. Hierarchical Inheritance: Multiple child classes inherit from a single parent class. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 22 / 49
- 23. Inheritance Example ofSingle Inheritance Single Inheritance Example 1 # Parent class 2 class Animal: 3 def __init__(self , name): 4 self.name = name 5 6 def speak(self): 7 return f{self.name} makes a sound 8 9 # Child class inheriting from Animal 10 class Dog(Animal): 11 def speak(self): 12 return f{self.name} barks 13 14 #Creating objects of both classes 15 animal = Animal(Generic Animal) 16 dog = Dog(Buddy) 17 18 # Accessing methods 19 print(animal.speak ()) # Output: Generic Animal makes a sound 20 print(dog.speak()) # Output: Buddy barks Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 23 / 49
- 24. Inheritance Explanation ofCode Explanation of Code The class Animal is the parent class with the method speak(). The class Dog is a child class that inherits from Animal and overrides the speak() method. Objects of both classes are created, and the speak() method is called on each object, demonstrating polymorphism (method overriding). Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 24 / 49
- 25. Inheritance Example ofMultilevel Inheritance Multilevel Inheritance Example I Example of multilevel inheritance in Python: 1 # Parent class 2 class Vehicle: 3 def __init__(self , brand): 4 self.brand = brand 5 6 def info(self): 7 return fVehicle brand: {self.brand} 8 9 # Child class inheriting from Vehicle 10 class Car(Vehicle): 11 def __init__(self , brand , model): 12 super().__init__(brand) 13 self.model = model 14 15 def info(self): 16 return fCar brand: {self.brand}, model: {self.model} 17 18 # Another child class inheriting from Car Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 25 / 49
- 26. Inheritance Example ofMultilevel Inheritance Multilevel Inheritance Example II 19 class ElectricCar(Car): 20 def __init__(self , brand , model , battery_capacity): 21 super().__init__(brand , model) 22 self.battery_capacity = battery_capacity 23 24 def info(self): 25 return fElectric Car: {self.brand} {self.model}, Battery: {self.battery_capacity}kWh 26 27 # Creating an object of ElectricCar 28 my_ecar = ElectricCar(Tesla, Model S, 100) 29 print(my_ecar.info()) # Output: Electric Car: Tesla Model S, Battery: 100kWh Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 26 / 49
- 27. Inheritance Explanation ofCode Explanation of Code The Vehicle class is the parent class, Car is a child class, and ElectricCar is a child class of Car. The super() function is used to call the constructor of the parent class. Each class adds or overrides attributes and methods, demonstrating multilevel inheritance. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 27 / 49
- 28. Inheritance Advantages ofInheritance Advantages of Inheritance Promotes code reusability by inheriting methods and attributes from a parent class. Establishes relationships between classes, making it easier to maintain and understand the code. Enables method overriding, allowing child classes to modify the behavior of inherited methods. Supports polymorphism, making it easier to work with dierent classes through a common interface. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 28 / 49
- 29. Polymorphism Polymorphism Laltu Sardar (IAI,TCG Crest) Intro to Python Programming 29 / 49
- 30. Polymorphism What isPolymorphism? What is Polymorphism? Polymorphism is one of the key principles of Object-Oriented Programming (OOP). It refers to the ability of dierent classes to be treated as instances of the same class through a common interface. Polymorphism allows methods to be used interchangeably between dierent types of objects, as long as they implement the same method signature. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 30 / 49
- 31. Polymorphism Types ofPolymorphism Types of Polymorphism Compile-time Polymorphism: Also called method overloading, but Python does not support this directly. Run-time Polymorphism: Achieved through method overriding, where the child class modies the behavior of the parent class's method. Python also supports polymorphism through duck typing, where the type or class of an object is less important than the methods it denes. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 31 / 49
- 32. Polymorphism Polymorphism withMethod Overriding Method Overriding Example Example of polymorphism with method overriding in Python: 1 # Parent class 2 class Animal: 3 def speak(self): 4 return Animal makes a sound 5 6 # Child class overriding speak method 7 class Dog(Animal): 8 def speak(self): 9 return Dog barks 10 11 class Cat(Animal): 12 def speak(self): 13 return Cat meows 14 15 # Polymorphism in action 16 animals = [Animal (), Dog(), Cat()] 17 18 for animal in animals: 19 print(animal.speak ()) # Output depends on the object type Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 32 / 49
- 33. Polymorphism Explanation ofCode Explanation of Code The Animal class denes a general speak() method. The Dog and Cat classes override the speak() method to provide their specic implementations. The same method speak() is called on dierent objects in the animals list, but the behavior changes based on the object's class. This demonstrates run-time polymorphism, where the method call is determined by the type of the object at runtime. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 33 / 49
- 34. Polymorphism Polymorphism throughDuck Typing Duck Typing Example I Python allows polymorphism through duck typing. If an object implements a required method, its type doesn't matter. 1 class Bird: 2 def fly(self): 3 return Bird flies 4 5 class Airplane: 6 def fly(self): 7 return Airplane flies 8 9 class Fish: 10 def swim(self): 11 return Fish swims 12 13 # Polymorphism using duck typing 14 def make_it_fly(entity): 15 print(entity.fly()) 16 Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 34 / 49
- 35. Polymorphism Polymorphism throughDuck Typing Duck Typing Example II 17 bird = Bird() 18 airplane = Airplane () 19 20 make_it_fly(bird) # Output: Bird flies 21 make_it_fly(airplane) # Output: Airplane flies 22 23 # make_it_fly(Fish()) # This will raise an AttributeError as Fish does not have fly method Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 35 / 49
- 36. Polymorphism Explanation ofDuck Typing Code Explanation of Duck Typing Code Both Bird and Airplane classes have the fly() method, so they can be passed to the make_it_fly function. This is an example of duck typing: If it looks like a duck and quacks like a duck, it's a duck. The function does not care about the actual type of the object, only whether it has the required method. Attempting to pass an object without the fly() method (like Fish) will raise an error. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 36 / 49
- 37. Polymorphism Advantages ofPolymorphism Advantages of Polymorphism Allows for exible and reusable code by allowing the same interface to be used for dierent underlying forms (data types). Makes it easier to add new classes with minimal changes to existing code. Reduces the complexity of programs and enhances the maintainability of the code. Promotes code organization by allowing objects of dierent types to be handled uniformly. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 37 / 49
- 38. Abstraction Abstraction Laltu Sardar (IAI,TCG Crest) Intro to Python Programming 38 / 49
- 39. Abstraction What isAbstraction? What is Abstraction? Abstraction is one of the core principles of Object-Oriented Programming (OOP). It refers to hiding the complex implementation details of an object and exposing only the essential features. Abstraction allows focusing on what an object does instead of how it does it. In Python, abstraction is typically achieved through abstract classes and interfaces. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 39 / 49
- 40. Abstraction Abstract Classesin Python Abstract Classes in Python An abstract class in Python is a class that cannot be instantiated and serves as a blueprint for other classes. It can have abstract methods that must be implemented by subclasses. Abstract classes are implemented using the abc module in Python. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 40 / 49
- 41. Abstraction Example ofAbstract Class Abstract Class Example I Example of an abstract class in Python: 1 from abc import ABC , abstractmethod 2 3 # Abstract class 4 class Shape(ABC): 5 @abstractmethod 6 def area(self): 7 pass 8 9 @abstractmethod 10 def perimeter(self): 11 pass 12 13 # Concrete class inheriting from abstract class 14 class Rectangle(Shape): 15 def __init__(self , width , height): 16 self.width = width 17 self.height = height 18 Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 41 / 49
- 42. Abstraction Example ofAbstract Class Abstract Class Example II 19 def area(self): 20 return self.width * self.height 21 22 def perimeter(self): 23 return 2 * (self.width + self.height) 24 25 # Creating an object of Rectangle 26 rect = Rectangle(5, 10) 27 print(fArea: {rect.area()}) # Output: Area: 50 28 print(fPerimeter: {rect.perimeter ()}) # Output: Perimeter: 30 Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 42 / 49
- 43. Abstraction Explanation ofAbstract Class Example Explanation of Code The Shape class is an abstract class that denes two abstract methods: area() and perimeter(). The Rectangle class inherits from Shape and provides concrete implementations for the area() and perimeter() methods. Abstract methods in the Shape class must be implemented in the child class, otherwise, the child class cannot be instantiated. This demonstrates how abstraction is achieved by hiding unnecessary details and only exposing the interface for calculating area and perimeter. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 43 / 49
- 44. Abstraction Use ofAbstraction in Python Use of Abstraction Abstraction allows dening common interfaces for dierent subclasses. It improves code modularity and extensibility by separating the what from the how. It promotes code maintainability by providing a clear interface and allowing changes to the internal implementation without aecting the external code. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 44 / 49
- 45. Abstraction Real-World Exampleof Abstraction Real-World Example of Abstraction I Another real-world example of abstraction using abstract classes: 1 from abc import ABC , abstractmethod 2 3 # Abstract class 4 class Device(ABC): 5 @abstractmethod 6 def turn_on(self): 7 pass 8 9 @abstractmethod 10 def turn_off(self): 11 pass 12 13 # Concrete class 1 14 class TV(Device): 15 def turn_on(self): 16 print(TV is now ON) 17 18 def turn_off(self): Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 45 / 49
- 46. Abstraction Real-World Exampleof Abstraction Real-World Example of Abstraction II 19 print(TV is now OFF) 20 # Concrete class 2 21 class Radio(Device): 22 def turn_on(self): 23 print(Radio is now ON) 24 25 def turn_off(self): 26 print(Radio is now OFF) 27 # Using abstraction 28 def use_device(device): 29 device.turn_on () 30 device.turn_off () 31 # Creating objects of TV and Radio 32 tv = TV() 33 radio = Radio() 34 35 use_device(tv) # Output: TV is now ON, TV is now OFF 36 use_device(radio) # Output: Radio is now ON, Radio is now OFF Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 46 / 49
- 47. Abstraction Explanation ofReal-World Example Explanation of Real-World Example The abstract class Device denes two abstract methods: turn_on() and turn_off(). Both TV and Radio provide their specic implementations for these methods. The use_device function demonstrates abstraction by operating on objects of both TV and Radio classes without needing to know the internal details of each device. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 47 / 49
- 48. Abstraction Advantages ofAbstraction Advantages of Abstraction Reduces complexity by hiding implementation details and exposing only essential functionalities. Promotes code reusability and reduces code duplication by dening common interfaces for subclasses. Helps in achieving a modular and maintainable codebase. Facilitates exibility by allowing changes to internal implementations without aecting other parts of the system. Laltu Sardar (IAI, TCG Crest) Intro to Python Programming 48 / 49
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