Python OOPs Concepts: Using Variables and Methods

 

Types of Variables in OOPs Python

	Instance Variable	Static Variable	Local Variable
	Object Level Variables	Class Level Variables	Method Level Variables
When to use:	For Every Object if you want Separate copy, use Instance Variables	For all object one copy is required, use static variables	Inside method, Just used for temporary requirement
Where to Declare	Inside the constructor method (in general)	Within the class directly, outside of methods (in general)	Within the method only.
How to Declare	Within the constructor: Instance variables can be declared within the constructor method using the self.   Using default values: Instance variables can be assigned default values during initialization.   Outside the class: use object name.	·         Within the class directly ·         Inside the classmethod: cls or classname ·         Remaining Places: By using classname	Only inside the method
How to access	Using self, Object Reference. (Inside the class, use self, outside the class use object name)	Using classname, cls, self,  Object reference	Only inside the method
How to Modify or update	can be accessed and modified from any other method within the class using the self keyword. Outside the class: use object name	Can be modified by using classname or cls	Can not be accessed / modified from outside of the method
How to Delete	Use self or object name	Use classname or cls	Delete inside the method directly using del

 

Types of methods

	Instance Methods	Class Methods	Static Methods
	Object Related Method	Class Related Method	General Utility Method
	this method is always talks about a particular object.	Method always talks about class level and common to all instances of the class	No way related to any object or class.
Variables used in the method	Using at least one instance variable (whether using static variables or not)	not using any instance variable, but using static variables and or local variables	Not using any instance variables and static variables. Using only local variables
	Use Instance Variable (must) + static variable (Optional) + local variable (Optional)	Use Static variable + local variable	Use only local variable
First Argument of the method	First argument to the instance method is always self, which is the reference variable to the current object.	First argument to the class method is always cls, which is the reference variable to class level object	No to self No to cls
Decorators used	No decorators are used	@classmethod decorator is used	@staticmethod decorator is used

 

Access Specifiers

In Python, access specifiers are used to control the visibility and accessibility of class attributes and methods. There are three main access specifiers in Python: public, protected, and private.

 

public:

·         Attributes and methods marked as public can be accessed from anywhere, both within the class and outside of it.

·         By default, all members in a Python class are public.

·         Members declared as public have a NO underscore prefix in their names. (ex: area, square())

protected:

·         Attributes and methods marked as protected are intended to be used only within the class and its subclasses.

·         Members declared as protected have a single underscore prefix in their names( ex: _method())

·         These members are not directly accessible from outside the class, but they can still be accessed within derived classes.

·         The use of protected members is generally discouraged in Python

private:

·         Attributes and methods marked as private are intended to be used only within the class.

·         In Python, private access is indicated by two underscores before the attribute or method name (e.g. __attribute or __method()).

·         These members are not directly accessible from outside the class, but they can still be accessed using the _classname__membername syntax. This is known as name mangling