Introductory Concept of Abstraction in Python

 

Introductory Concept of Abstraction in Python

* In languages like Java , there are several keywords like private , public and protected in order to implement the various levels of abstraction . These keywords are called as Access Specifiers .

* In Python , such kind of Access Specifiers are not available .

* Everything written inside the class comes under the category of public – that means all the objects , methods , variables present within any class in Python can be considered to be coming under Public Category which means that everything which is written inside a class is available outside the class to other people .

* Suppose , one does not want to make a variable outside the class or to other members inside the class , then we can write the variable with two double scores before it as : _var . This is like a private variable in Python .

* In the following example , 'y' is a private variable since it is written as : __y

class MyClass:

    def _init_(self):

        self.__y = 3

* Now , it is not possible to access the variables from within the class or outside of the class as :

m = MyClass()

print(m.y)

* The preceding print() statement displays an error message as : AttributeError :'MyClass' object has no attribute 'y' .

* Even though one can not access the private variable in this way .. however , it is possible to access it in the format :

instancename.__Classname_var

* This means that we are using the Classname differently to access the private variable . This concept is known as name mangling . In name mangling , one needs to use one underscore before the classname and two underscores after the classname . Like this , using the names differently to access the private variables is called as name mangling .

 * For example , in order to display a private variable 'y' value one can write the following code :

 print(m._MyClass_y)

The same statement can be written inside the method as :

print(self._MyClass_z) . When we use single underscore before a variable as _var , then that variable or object will not be imported into other files .