Data Hiding in Python

Data hiding is also known as data encapsulation and it is the process of hiding the implementation of specific parts of the application from the user. Data hiding combines members of class thereby restricting direct access to the members of the class.

Data hiding plays a major role in making an application secure and more robust.

Data Hiding in Python

Data hiding in Python is a technique of preventing methods and variables of a class from being accessed directly outside of the class in which the methods and variables are initialized. Data hiding of essential member functions prevents the end user from viewing the implementation of the program hence increasing security. The use of data hiding also helps in reducing the complexity of the program by reducing interdependencies.

Data hiding in Python can be achieved by declaring class members as private by putting a double underscore (__) as prefix before the member name.

Syntax

The syntax for hiding data in Python is as follows ?

__variablename

Example 1 - Without Class Name

In this example, data hiding is performed by declaring the variable in the class as private ?

class Hidden: 
    # declaring private member of class 
    __hiddenVar = 0 
    
    def sum(self, counter): 
        self.__hiddenVar += counter 
        print(self.__hiddenVar) 

hiddenobj = Hidden() 
hiddenobj.sum(5) 
hiddenobj.sum(10) 

# print statement throws error as __hiddenVar is private 
print(hiddenobj.__hiddenVar)

5
15
Traceback (most recent call last):
  File "main.py", line 12, in module
    print(hiddenobj.__hiddenVar)
AttributeError: 'Hidden' object has no attribute '__hiddenVar'

Example 2 - With Class Name

In the following example, the hidden data can be accessed directly outside the class using name mangling ?

class Hidden:
    # declaring hiddenVar private by using __
    __hiddenVar = 0
    
    def sum(self, counter):
        self.__hiddenVar += counter
        print(self.__hiddenVar)

hiddenobj = Hidden()
hiddenobj.sum(5)
hiddenobj.sum(10)

# adding class name before variable to access the variable outside the class
print(hiddenobj._Hidden__hiddenVar)

5
15
15

Example 3 - Private and Protected Members

Let's look at another example of data hiding using both private and protected members of the class ?

class Employee:
    # Hidden members of the class
    __password = 'private12345'  # Private member
    _id = '12345'  # Protected member
    
    def Details(self):
        print("ID:", self._id)
        print("Password:", self.__password + "\n")

hidden = Employee()
hidden.Details()
print(hidden._Employee__password)

ID: 12345
Password: private12345

private12345

In the above output, the Details function is part of Employee class, hence it can access both the private and protected members of the class. That is why id and password can be accessed without use of class name. However, in the final print statement, class name is required to access password since scope of private members is restricted within the Employee class.

Name Mangling

Python performs name mangling for private attributes. When you declare __variablename, Python internally changes it to _Classname__variablename. This is why private variables can still be accessed using the mangled name.

Advantages of Data Hiding

Conclusion

Data hiding in Python is achieved using double underscore (__) prefix for private members. While Python doesn't enforce true privacy, name mangling provides a level of encapsulation that helps maintain code structure and security.