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 classclass 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 classobj.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.
