basic concepts of object oriented in python
- 2. Introduction • Python is an object-oriented programming language. This means that almost all the code is implemented using a special construct called classes. • Python offers classes, which are a effective tool for writing reusable code. To describe objects with shared characteristics and behaviors, classes are utilized.
- 3. Class • A class is a user-defined data type that contains both the data itself and the methods that may be used to manipulate it. • In a sense, classes serve as a template to create objects. They provide the characteristics and operations that the objects will employ.
- 4. Object • An object is an instance of a class. We use the object of a class to perform actions. • Objects have two characteristics: They have states and behaviors (object has attributes and methods attached to it) Attributes represent its state, and methods represent its behavior.
- 6. Syntax for Class class class_name: class attributes/members class methods
- 7. Syntax for object object_name = Class_Name(arguments) OR object_name = Class_Name()
- 8. Example Class name Method Attribute Call parameter using Class name
- 9. Example object name Method Attribute Call parameter using object Class name
- 10. Important Note • Class attributes are always public and can be accessed using the dot (.) operator and object name. • Class methods must have an extra first parameter in the method definition. We do not give a value for this parameter when we call the method, Python provides it.
- 11. Self parameter • The self parameter is a reference to the current instance of the class, and is used to access variables that belongs to the class. • It does not have to be named self , you can call it whatever you like, but it has to be the first parameter of any function in the class.
- 12. Class Method • classmethod() methods are bound to a class rather than an object. Class methods can be called by both class and object. These methods can be called with a class or with an object.
- 13. Constructor¶ • In object-oriented programming, A constructor is a special method used to create and initialize an object of a class. • This method is defined in the class. • The constructor is executed automatically at the time of object creation. • The method the __init__() simulates the constructor of the class.
- 15. Rules for constructor • For a class, it allows only one constructor. • The constructor name must be __init__. • A constructor must be defined with an instance attribute (nothing but specifying the self keyword as a first parameter). • It cannot return any value, except None.
- 16. Types of constructor Default constructor: Python will provide a default constructor if no constructor is defined. It does not perform any task but initializes the objects. It is an empty constructor without a body. This constructor is known as the default constructor. The default constructor is a simple constructor which doesn’t accept any arguments. Its definition has only one argument which is a reference to the instance being constructed.
- 17. Types of constructor Parameterized constructor: Constructor with parameters is known as parameterized constructor. The parameterized constructor takes its first argument as a reference to the instance being constructed known as self and the rest of the arguments are provided by the programmer.
- 18. Types of constructor Non-Parameterized constructor: A constructor without any arguments is called a non-parameterized constructor. This type of constructor is used to initialize each object with default values. This constructor doesn’t accept the arguments during object creation. Instead, it initializes every object with the same set of values.
- 19. Constructor With Default Values • Python allows us to define a constructor with default values. The default value will be used if we do not pass arguments to the constructor at the time of object creation.
- 20. Benefits of constructor • Initialization of objects • Easy to implement • Better readability • Encapsulation
- 21. Disadvantages of constructor • Overloading not supported: This means that you cannot have multiple constructors with different parameters in a single class. • Limited functionality: Python does not have constructors with access modifiers like public, private or protected.
- 22. Destructor Destructor is a special method that is called when an object gets destroyed. On the other hand, a constructor is used to create and initialize an object of a class. The __del__() method is a known as a destructor method in Python. In Python, destructors are not needed as much as in C++ because Python has a garbage collector that handles memory management automatically.
- 24. ENCAPSULATION ▶Encapsulation is one of the fundamental concepts in OOP. ▶It describes the idea of wrapping data and the methods that work on data within one unit. ▶This puts restrictions on accessing variables and methods directly and can prevent the modification of data. ▶Using encapsulation,we can hide an object’s internal representation from outside.This is called information hiding.
- 25. ACCESS MODIFIERS IN PYTHON Encapsulation can be achieved by declaring the data members and methods of a class either as private or protected.
- 26. Private Member • To define a private variable add two underscores as a prefix at start of a variable name. • Private members are accessible only within the class and we can’t access them directly from the class objects.
- 27. Protected Member ▶ Protected members are accessible within the class and also available to its sub-classes. ▶ To define a protected member,prefix the member name with a single underscore _.