Protected variable in Python

Last Updated : 10 Jan, 2020

Prerequisites: Underscore ( _ ) in Python

A Variable is an identifier that we assign to a memory location which is used to hold values in a computer program. Variables are named locations of storage in the program. Based on access specification, variables can be public, protected and private in a class.

Protected variables are those data members of a class that can be accessed within the class and the classes derived from that class. In Python, there is no existence of “Public” instance variables. However, we use underscore ‘_’ symbol to determine the access control of a data member in a class. Any member prefixed with an underscore should be treated as a non-public part of the API or any Python code, whether it is a function, a method or a data member.

Example 1:

# program to illustrate protected 
# data members in a class  
  
  
# Defining a class 
class Geek:  
      
    # protected data members  
    _name = "R2J"
    _roll = 1706256
      
    # public member function  
    def displayNameAndRoll(self):  
  
        # accessing protected data members  
        print("Name: ", self._name)  
        print("Roll: ", self._roll)  
  
  
# creating objects of the class          
obj = Geek()  
  
# calling public member  
# functions of the class  
obj.displayNameAndRoll()  

Output:

Name:  R2J
Roll:  1706256

Example 2: During Inheritance

# program to illustrate protected 
# data members in a class  
  
  
# super class  
class Shape:  
      
    # constructor  
    def __init__(self, length, breadth):  
        self._length = length 
        self._breadth = breadth  
          
    # public member function  
    def displaySides(self):  
  
        # accessing protected data members  
        print("Length: ", self._length)  
        print("Breadth: ", self._breadth)  
  
  
# derived class  
class Rectangle(Shape):  
  
    # constructor  
    def __init__(self, length, breadth):  
  
        # Calling the constructor of 
        # Super class 
        Shape.__init__(self, length, breadth)  
          
    # public member function  
    def calculateArea(self):  
                      
        # accessing protected data members of super class  
        print("Area: ", self._length * self._breadth)  
                      
  
# creating objects of the  
# derived class          
obj = Rectangle(80, 50)  
  
# calling derived member  
# functions of the class 
obj.displaySides() 
  
# calling public member 
# functions of the class  
obj.calculateArea()  

Output:

Length:  80
Breadth:  50
Area:  4000

In the above example, the protected variables _length and _breadth of the super class Shape are accessed within the class by a member function displaySides() and can be accessed from class Rectangle which is derived from the Shape class. The member function calculateArea() of class Rectangle accesses the protected data members _length and _breadth of the super class Shape to calculate the area of the rectangle.