This document discusses object-oriented programming concepts in Python including classes, objects, attributes, methods, inheritance, and method overriding. It defines a MyVector class with x and y attributes and methods to add vectors and display their count. Access specifiers like private and built-in are covered. Python uses garbage collection and has no destructors. Inheritance allows a SubVector class to extend MyVector, and a method can be overridden to change a class's behavior.

1. Python – Object Oriented Programming
by Raghunath Akula

2. Classes & Objects
 Class serves as the primary means of abstraction in Object-Oriented
programing.
 A class provides a set of behaviors in the form of member_functions /
methods, with implementation that are common to all instance.
 In class, the state information for each instance is represented in the
form of Attributes / Data members.
 Instances are objects that are created which follow the definition given
inside of the class.
 No separate class interface definition.
class MyVector:
def __init__(self, x, y):
self . x = x
self . y = y
def __add__(self, param2):
return MyVector(self.x + param2.x, self.y + param2.y)
Obj1 = MyVector(1, 2) “Object initiation for MyVector class.”

3. Access Specifiers
 Python provides a number of access modifiers to help you set the level
of access for attributes and methods.
 Private - 2 leading under-scores in its name, but none at the end. Can’t
be accessed outside of class
 Built-in – Methods or attributes having 2 underscores at the beginning
and the end.
 Doesn’t support ‘protected’. Subclasses would be unable to access these
private data either.
Garbage Collector
 Python has automatic garbage collection.
 Will automatically detect when all of the references to a piece of
memory have gone out of scope. Automatically frees that memory.
 There’s also no Destructor method for classes

4. Methods
 Define a method in a class by including function definitions within the
scope of the class block
 There must be a special first argument self in all of method definitions
which gets bound to the calling instance
 There is usually a special method called __init__ in most classes
class MyVector:
count = 0 “Class attribute”
def __init__(self, x, y):
self . x = x
self . y = y
def __add__(self, param2):
return MyVector(self.x + param2.x, self.y + param2.y)
def displayCount(self):
count = self.x + self.y
return count
Obj1 = MyVector(1, 2) “Object initiation for MyVector class.”
print Obj1.displayCount() “Calling displayCount method.”

5. Constructor ( __init__ )
 Serves as a constructor for a class.
 The arguments passed to the class are given to its __init__() method
def __init__(self, x, y):
self . x = x
self . y = y
self
 The first argument of every method is a reference to the current instance of
the class
 Parameter object self refers to current object being created, similar to
keyword this in Java
 Although self explicitly mentioned when defining the method, not mandatory
included while calling the method. Self parameter is passed automatically by
python.

6. Attributes
Two Kinds of Attributes:
(1)Data Attributes
Owned by particular instance of a class.
Each instance has its own value for it.
(2)Class Attributes
All instance inside class share the same value for it.
Similar to static variables or class-wide constants.
“Example: Data Attributes”
class MyVector:
def __init__(self, x, y):
self . x = x
self . y = y
“Example: Class Attributes”
class MyVector:
count = 0 “static variable”
def displayCount(self):
count = self.x + self.y
return count

7. Inheritance
 A class can extend the definition of another class
 Allows to use methods and attributes already defined in the previous
classes.
 To define a subclass, put the name of the superclass in parentheses
“(…)”.
 Python has no ‘extends’ keyword like Java. Python supports multiple
inheritance.
“Extending MyVector class”
class SubVector (MyVector):
def __init__(self, sub_x, sub_y):
self . x = sub_x
self . y = sub_y
def displayCount(self):
count = self.x + self.y
return count

8. Method Overriding
 Overriding is a very important part of OOP. It has the ability of a
class to change the implementation of a method provided by one of its
ancestors.
 Python inheritance works through implicit delegation – when the object
cannot satisfy a request, it forward request to its ancestors.
“Parent Class”
class MyVector:
def __init__(self, x, y):
self . x = x
self . y = y
def displayCount(self):
return self.x + self.y
“Child Class”
class SubVector (MyVector):
def displayCount(self): “Overriding dispalyCount method”
return self.x + 10

9. Thank you!!