'OOPS' stands for Object Oriented Programming System

Firstly, comes classes.

Classes are blueprint or skeleton or overall definition of OOPs things.

Eg. If I say there is a car, and ask you to sit inside. Then you will ask which one? Because there are many cars so u're confused.

You've probably understood meaning of car, it has 4 wheels, engine, brake, steering, etc. But which one? That you know only when I say u its color, model name, company name, etc.

So basically, 'car' is a skeleton or blueprint over here. So, u know its basic properties (4 wheels, steering, gear, brakes, etc). But u dont know the specific properties (color, model name, company, etc)

In short,

Class is a classification of real world entity.

Code:

a = 1

print(type(a))

o/p:

<class 'int'>

here, we get class integer as output, not the number.

Code:

print(type("PWSKILLS"))

o/p:

<class 'str'>

Similarly, we get class string here, but not the value.

Class is a blueprint of real world entity but not a specification of real world entity.

Object:

It is a real world entity/real world instance.

Code:

a = 1

Here, a is object or instance or variable of the integer class.

Creating a class:

use the 'class' keyword, which is a reserved keyword in Python Language.

Code:

class test :

o/p:

  Cell In[4], line 1
    class test :
                ^
SyntaxError: incomplete input

Error in output, bcoz there is nothing inside class which is not allowed.

So we put 'pass' to create blank class.

Code:

class test : pass

Why OOPs?

Because it makes the code reusable, structured and easy to use.

You can put variables, functions, modules inside class.

Creating object of class:

Code:
a = test()
type(a)

o/p:

__main__.test

its type is 'test'

Suppose we create a class with a method inside it:

class karanskills: def welcome_msg(): print("Welcome to class")

and we create variable 'rohan' of that class:

rohan = karanskills()

then we check type of it:

print(type(rohan))

o/p:

<class '__main__.karanskills'>

here, 'rohan' belongs to the type of class : karanskills

Now we try to call welcome_msg() method from object:

rohan.welcome_msg()

o/p:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[4], line 1
----> 1 rohan.welcome_msg()

TypeError: karanskills.welcome_msg() takes 0 positional arguments but 1 was given

Error is shown; It says 1 argument assgined but we haven't assgined any. then why did this happen?

Whichever method you define inside the class, you need to bind it / point it to the class so class can understand that it is own method of class.

For that u write word 'self'.
so, whenever you write a function inside a class, firstly, write 'self' with the function.

New Code:

class karanskills: def welcome_msg(self): print("Welcome to class")

rohan = karanskills()

rohan.welcome_msg()

o/p:

Welcome to class

Same with another object:

gaurav = karanskills()

gaurav.welcome_msg()

o/p:

Welcome to class