Python Class and Object
Python is an object-oriented programming language. Unlike
procedure-oriented programming, where the main emphasis is on
functions, object-oriented programming stress on objects.
The object is simply a collection of variables and methods
(functions) that act on those data. And, class is a blueprint for the
object.
We can think of a class as a sketch of a house. It contains all the
details about the floors, doors, windows, etc. Based on these
descriptions we build the house. House is the object.
Class
A class is a blueprint for any functional entity which defines its
properties and its functions. Classes are a user-defined data type
that is used to encapsulate data and associated functions together. It
also helps in binding data together into a single unit. Like Human
Being, having body parts and performing various actions.
In Python, a class is defined by using a keyword class like a
function definition begins with the keyword def.
Class Syntax
class ClassName:
Statements
The Statements consists of all the component statements defining
class members, data attributes, and functions.
Example:
class abc:
a=20
print (a)
Output:
Object
The object is an entity that has a state and behavior. It may be
anything. It may be physical and logical. We can create new object
instances of the classes. The procedure to create an object is similar
to a function call.
Object Syntax
This will create a new instance object named obj. We can
access attributes of objects using the object name prefix.
Attributes may be data or methods. The method of an object is the corresponding functions of that class. Any function object that is a class attribute defines a method for objects of that class.
Example:
class abc:
def fun(self):
print ("Class and object")
obj=abc()
obj.fun()
Output:
You may have noticed the self parameter in function definition
inside the class but, we called the method simply as obj. fun()
without any arguments. This is because, whenever an object calls
its method, the object itself is passed as the first argument.
self Parameter
The self parameter is a reference to the class itself and is used
to access variables that belong to the class.
It does not have to be named self, you can call it whatever you
like, but it has to be the first parameter of any function in the class.
The __init__() Function
To understand the meaning of classes we have to understand
the built-in __init__() function.
All classes have a function called __init__(), which is always
executed when the class is being initiated.
Use the __init__() function to assign values to object
properties, or other operations that are necessary to do when the the object is being created.
Example:
class abc:
def __init__(self,a,b):
self.a=a
self.b=b
def fun(self):
print ("Value of A is", self.a,"and B is", self.b)
obj=abc(10,20)
obj.fun()
Output:
Value of A is 10 and B is 20
Example:
class abc:
def __init__(self,a,b):
self.a=a
self.b=b
def fun(self):
print ("Value of A is", self.a,"and B is", self.b)
obj=abc(10,20)
obj.fun()
obj=abc(100,200)
obj.fun()
Output:
Value of A is 10 and B is 20
Value of A is 100 and B is 200
