22 Feb Python Classes and Objects
Python is an interpreted high-level, structural, and object-oriented programming language. Since it is object-oriented, the concept of classes and objects is well-discussed and implemented. A class is the basis of object-oriented programming in Python. In this tutorial, we will learn about Classes and Objects in Python. A class is a template for an object, whereas an object is an instance of a class.
What is a class in Python
As discussed above, a class is a blueprint for objects in Python. We can easily create a class like this:
class name_of_class: # Statement1 # Statement2 # Statement3 . . . StatementN
Class Definition in Python
The class keyword is used to create a class in Python. The class is a reserved word in Python. In the example below, we will see how to create a class in Python:
Demo85.py
# creating a class with a property val # the class keyword is used to create a class class Studyopedia: val = 100 print(Studyopedia)
Output
<class '__main__.Studyopedia'>
What is an object in Python?
An object is an instance of a class i.e. object is created from a class. An object represents real-life entities, for example, a Bike is an object. The object has State, Behavior, and Identity:
- Identity: Name of Bike
- State (Attributes): The data of the object Bike i.e. Color, Model, Weight, etc.
- Behavior (Methods): Behavior of object Bike like to Drive, Brake
Let us now see the representation, with Bike as an object:
How to Create an Object in Python
Considering the above example of classes in Python, we can easily create an object.
Demo86.py
# creating a class with a property val
# the class keyword is used to create a class
class Studyopedia:
val = 100
print(Studyopedia)
# object ob
ob = Studyopedia()
# displaying the value using the object ob
print("Value = ",ob.val)
Output
<class '__main__.Studyopedia'> Value = 100
Now, we can easily create a sample Python program on Classes and Objects. Let’s see.
Example – Python Classes and Objects
Demo87.py
# class
class Bike:
# attributes of Bike
name = "Hayabusa"
body = "GEN III"
engine = 1340
# Custom Python function
def demoFunc(self):
print("\nBike = ", self.name)
print("Body = ", self.body)
print("Engine (cc) = ", self.engine)
# Objects
b1 = Bike()
b2 = Bike()
# Accessing using the 1st object
print("Bike name = ",b1.name)
print("Bike Engine = ",b1.engine)
# calling using the 2nd object
b2.demoFunc()
Output
Bike name = Hayabusa Bike Engine = 1340 Bike = Hayabusa Body = GEN III Engine (cc) = 1340
Python _init_() Function
The classes in Python have __init__() function. Like constructors in Java, the __init__() function executes when the object gets created. Using this method, easily assign values to object properties.
Let us understand with an example, wherein we will create a class Students and values will be assigned using the __init__(). We have also created object functions:
Demo88.py
class Students:
# using the __init__ function
def __init__(self, sname, ssub, sgrade):
self.sname = sname
self.ssub = ssub
self.sgrade = sgrade
# custom function
def demofunc(self):
print("I am " + self.sname)
print("I am interested in the Subject " + self.ssub)
# creating 3 objects for class Students
st1 = Students("Amit", "Programming", "A+")
st2 = Students("Rohit", "Science", "A")
st3 = Students("Shreyas", "Math", "B+")
# calling the custom function using objects
st1.demofunc()
st2.demofunc()
st3.demofunc()
Output
I am Amit I am interested in the Subject Programming I am Rohit I am interested in the Subject Science I am Shreyas I am interested in the Subject Math
Above, we have also used the self parameter. The class methods in Python have the first parameter as self to access the class variable. A method with no argument should also have an argument self However, we can give it any name. It is not mandatory to use the word self.
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