Day 9 : Encapsulation and polymorphism

Hello Guys,
previously we learn about constructor and inheritance and basics of python.

Today we learn about  encapsulation and polymorphism.

Encapsulation

Encapsulation is wrapping data and the methods that work on data within one unit. This puts restrictions on accessing variables and methods directly and can prevent the accidental modification of data.

To prevent accidental change, an object’s variable can only be changed by an object’s method. Those type of variables are known as private varibale.

Protected members

Protected members (in C++ and JAVA) are those members of the class which cannot be accessed outside the class but can be accessed from within the class and it’s subclasses.
Public, private and protected keyword
But

To accomplish this in Python, just follow the convention by prefixing the name of the member by a single underscore “_”.

Code :

class Base:

    def __init__(self):

          

        # Protected member

        self._a = 2

  

# Creating a derived class    

class Derived(Base):

    def __init__(self):

          

        # Calling constructor of

        # Base class

        Base.__init__(self) 

        print("Calling protected member of base class: ")

        print(self._a)

          

obj1 = Base()

Output:

Calling protected member of base class: 
2

Private members

Private members are similar to protected members, the difference is that the class members declared private should neither be accessed outside the class nor by any base class. In Python, there is no existence of Private instance variables that cannot be accessed except inside a class. However, to define a private member prefix the member name with double underscore “__”.

Code : 

class Base:

    def __init__(self):

        self.a = "GeeksforGeeks"

        self.__c = "GeeksforGeeks"

  

# Creating a derived class

class Derived(Base):

    def __init__(self):

          

        # Calling constructor of

        # Base class

        Base.__init__(self) 

        print("Calling private member of base class: ")

        print(self.__a)

# Driver code

obj1 = Base()

print(obj1.a)




Output :

GeeksforGeeks

Polymorphism

The word polymorphism means having many forms. In programming, polymorphism means same function name (but different signatures) being uses for different types.

Code:

def add(x, y, z = 0): 

    return x + y+z

  

# Driver code 

print(add(2, 3))

print(add(2, 3, 4))




Output:

5
9

Watch this for method overriding Check here







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