Object

In the object-oriented programming (OOP), an object is an instance of a class, which is a template or a model that defines a set of attributes and methods (behaviours). The objects combine data and behaviour into a single entity, facilitating the organisation and manipulation of the code. This programming style, known as object-oriented OOP, is key to programming modern for its ability to simplify the software development and improve the code reuse.

Fundamental concepts 

• ClassA class is a definition of a type of object. It acts as a template for creating objects, specifying what attributes and behaviours will have. For example, a Car class could have attributes such as colour, make and model, and methods such as start(), brake() and accelerate(). The classes and objects are data structures fundamental based on the concept to represent entities of the real world within the code.
• InstanceInstance: An instance is a concrete occurrence of a class. When you create an object, you are creating an instance of a class. For example, myCar = Car() creates an object myCar which is an instance of the class Car. This clearly answers the question what is an object in programmingis a specific entity created from a class.
• AttributesAttributes: These are the properties or data that are stored in an object. In the case of the object myCar, the attributes could be colour: red, brand: Toyota, model: Corolla. These are the properties and methods that define the behaviour of the object.
• Methodsare functions or procedures associated with an object that can perform actions using the object's attributes or modify their values. For example, myCar.start() could change the state of the car to “on”.

Characteristics of objects 

• EncapsulationObjects encapsulate data and methods, protecting data from direct access from outside the object and allowing manipulation only through defined methods. This helps maintain data integrity and facilitates code maintenance.
• InheritanceAllows one class to derive from another, inheriting its attributes and methods, and being able to add new ones or modify existing ones. For example, CocheElectrico could inherit from Coche and add a battery attribute and a charge() method.
• Polymorphism: Ability to use methods in the same way on different objects, even if those methods belong to different classes. This allows individual items of different classes are dealt with in a unified manner. Thus, the polymorphism allows a more flexible and adaptable design.
• AbstractionIt allows you to work with high-level concepts, hiding complex implementation details. This is achieved by defining classes and objects that represent real-world entities or abstract concepts. In this way it is possible to controlling the world of programming by means of comprehensible models.

Example of a Python object

Consider a system for managing a library. You could have a Book class with the following attributes and methods: 

Python code: 

class Libro: 

    def __init__(self, title, author, isbn): 

        self.title = title 

        self.author = author 

        self.isbn = isbn 

        self.prestado = False 

    def lend(self): 

        if not self.prestado: 

            self.prestado = True 

            print(f'The book {self.title} has been borrowed.’) 

        else: 

            print(f'The book {self.title} is already borrowed.’) 

    def return(self): 

        if self.prestado: 

            self.prestado = False 

            print(f'The book {self.title} has been returned.’) 

        else: 

            print(f'The book {self.title} was not borrowed.’) 

Here, Book is a class that defines how books are represented in the system. The attributes are title, author, isbn and lent, while the methods lend() and return() handle the lending status of the book. This is a clear example of how objects in Java or in any other of the object-oriented languages.

To use this class, you would create instances (objects) of Book: 

Python code: 

book1 = Book(‘1984’, ‘George Orwell’, ‘1234567890’) 

libro2 = Libro(‘Brave New World’, ‘Aldous Huxley’, ‘0987654321’) 

book1.lend() # Output: Book 1984 has been lent. 

book1.lend() # Output: Book 1984 is already lent. 

book1.return() # Output: Book 1984 has been returned. 

This example sums it up well what is object-oriented programming, what is POO, and how their OOP principles are applied in practice.