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Friends here our concept is

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class and object attributes.

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See already we know simply what is the class. So class is

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a template or blueprint to create an object.

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So once if you have a template from that we can create any

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number of objects. And class is the combination of attributes

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and methods. So basically attributes are like variables,

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[no audio]

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and we can define attributes for class and objects.

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I mean for class level we can define some variables, and for

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object level we can define some variables.

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Let me explain this concept with the help of a simple Python

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script. So I am saving my script name as 'working_on_attributes.py'.

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So guys suppose I am writing a simple Python script

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or program to maintain the data for employees.

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Suppose assume that for time being we are having some

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two employees.

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Right. Then,

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I want to maintain the data for these two employees, then

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before going to maintain the data first

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I will assume, I am going to create one template. So I want

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to store so and so things for employee.

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[no audio]

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Right. So then what I am doing is, 'class', simply 'emp'.

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That's it. ':', then enter.

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So I am defining

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one method to store

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the employee name, age and salary suppose.

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So let me define

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[no audio]

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as 'get_name_age_salary'.

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[no audio]

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That's it. So actually, this is a function.

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But whenever if you want to write a function inside of a

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class, you have to write by default 'self' as the key, and you

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don't need to worry about the value for 'self'. Automatically

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'self' will be replaced by the particular object. From which

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object you're calling that object will come in the place of 'self'.

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That's fine.

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Now you are expecting for this function 'name', 'age', and 'salary'.

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Let me take variables as, I mean I will pass arguments for

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this method while calling like 'name',

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'age' and 'salary'. That's it.

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Then I want to store this 'name', 'age', and 'salary' in a memory

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location. So for that you have to write 'self.name=name'.

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So guys don't get confused, 'self.name' is different, and

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'name' is different.

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It is like 'xy = y', completely they are different variables.

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Right. Then 'self.age = age'.

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So if you are getting confusion just take here arguments

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as different variables,

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I mean different names like 'n', 'a', 's', but if you take 'name',

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'age', 'salary', just somewhat meaningful

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that's why I'm taking arguments as 'name', 'age' and 'salary'. Then

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'self.salary'.

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That's it. Then I am going to define one more function just to display

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the employee details.

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Then what I can do, 'display_emp_details', or simply

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'display_details

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[no audio]

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(self)'. So actually to display employee details

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what we need? 'name', 'age', and 'salary'.

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So if you are using normal function like 'display_details',

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if it is a normal function, to get your details you need to

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pass arguments to this function, but this is a method and

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if you observe these two methods are in the same class, that's

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why whatever the variables you are having you define in your

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first method, those variables you can access in other method.

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That's why I'm not passing any arguments to 'display_details'

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method. Directly

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I can access from my previous method.

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So that's why directly

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what I am doing is, simply 'print(

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"The name is:". So simply here

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I will write 'name'. Name is nothing but 'self.name', but

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not this 'name' guys.

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This you're passing to this method while calling.

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Okay. But actual variables or attributes for your objects

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are these things.

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Then let me write "/n The age is: ", you can write anything.

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No problem. Just for your understanding

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I'm writing simple script. Then, "The salary is: ".

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[no audio]

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That's it. Let me write salary, 'self.salary'. That's it.

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Right. Then write simply 'return None'.

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[no audio]

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So I'm not expecting any return value from this method.

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So here also I'm not expecting any return value,

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that's why I'm writing simply 'return None'. That's fine.

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So guys, if you run your code as of now, you're not getting

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any output and you are not going to get any error because

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this is just a template. Templates won't execute whenever you

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run. It will execute whenever if you assign this template

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to any object.

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Right. That's fine.

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Now see that. Just assume that we are having two employees,

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say 'emp1' and 'emp2'.

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[no audio]

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Okay.

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Now I want to store the details for 'emp1' and 'emp2',

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and I want to see whenever if I need. So to store we have

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this method, and to display we have this method, second method.

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Right. So instead of 'get' let me 'assign', or yeah, no problem.

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You can take any method, right?

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So 'emp1'.

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So before going to store 'emp1' details, what you have to do?

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First of all, you need to assign this template for this object.

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Right. Then only these methods and these attributes or variables,

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you can access from 'emp1'.

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That's why, what I'm doing? First

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I am doing 'emp()', then for 'emp1()', and 'emp2()'.

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That's it.

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Right. So guys as of now you have 'emp1' and 'emp2'

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objects, but there is no information for 'emp1'

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and 'emp2'. Because, if you execute any one of the method,

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then only you're going to store your data. Suppose to store your data

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you have to execute this method, then you need to call that

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method. You know how to call a method of your class.

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Now, assume that this entire class, this template is stored

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in the name of 'emp1' and 'emp2'. So whenever if

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you call from 'emp1', 'emp1.get_name_age_salary'.

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Let's say I am giving as suppose

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'name', anything like John,

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[no audio]

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'age' suppose 34,

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then I am giving 'salary' as something like,

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[no audio]

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just assume it may be 45000 per month. Just assume that.

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Right. Fine.

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Now, the same way I want to store my data, my 'emp2' data, then

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just write

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[no audio]

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That's it. Okay.

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Now if I execute, while running your program somewhere in

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memory location two memory blocks will be created. One memory

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block for 'emp1' and second memory is for 'emp2'.

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Right. And see before calling your 'display' if I write 'dir(emp1)'

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See the result, what you are getting.

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[no audio]

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Basically for 'emp1', what are the information

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you are having? 'name',

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I mean this method and variables, right, and one more method

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here. Now see the output.

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Anyway, these are the default values.

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Other than that, see that. 'age' is there, 'name' is there, 'salary'

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is there. So 'emp1.age', 'emp1.name', 'emp1.salary'.

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The same way you can use, this is the method,

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these two are the methods. We know

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that. By observing here

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we can understand that these two are methods.

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So 'emp1.display_details()'.

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'emp1.get_name_age_salary'.

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But while calling if you need arguments, you need to pass.

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The same way you can also run this for

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'emp2'.

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[no audio]

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Same information is there for 'emp2' also

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but the values are different.

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That's it.

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Now fine. Just observe this guys. While calling from your 14th line

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or 'emp1.get_name_age_salary

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("John", 34, 45000)', values

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will be assigned to respectively 'name', 'age' and 'salary'. Then

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what about 'self'?

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'self' by default from which object you are calling, that object

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'name' will be stored in 'self'.

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That's why in memory it is going to create like

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'emp1.name' not 'self.name'.

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Okay. For our purpose, for dynamic purpose we are writing 'self',

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but while storing your values, your variables in memory location

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they are going to store in the respective by using 'emp1',

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'emp1.name', 'emp1.age', 'emp1.salary'.

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That's it. And one more thing, whenever you are accessing

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your variables inside of a class, always you have to take

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'self.name', 'self.age', 'self.salary', like that.

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But for same 'emp1'

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if you want to access your variables, attributes outside of

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a class, outside of a class, then you have to access with

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'emp1.' not 'self.'. Be clear. Outside you have to

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access with the 'emp1.'. Suppose

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I want to display 'age'. See the result what you are getting.

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34. That's fine.

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And if you observe even method we are also calling as

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'emp1.'. Suppose if I want to call

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'display' method, how can I call? 'emp1.display_details'. That's it.

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If you observe 'display_details' is not requiring any arguments,

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it is not taking any arguments except 'self'.

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Anyway, 'self' is going to store with the help of 'emp1'.

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'emp1.name' will store into 'self', that's why we are passing

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correct arguments while calling 'display' method.

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Now just observe the result.

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[no audio]

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And one more thing, you are calling your method outside of a class.

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Suppose I want to display my details after assigning the

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data to your 'self.name', 'age' and 'salary',

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then you have to call this method inside of this first method.

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So whenever if you want to call your method inside of a method

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then you have to write 'self.', method name.

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[no audio]

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So 'self' means outside you can assume this is like 'emp1',

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but inside of a class if you want to call and if you

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want to execute any method you have to write 'self.'. Now,

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let me comment this and see the result. You're going to get,

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'display_details' for two employees. See that.

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First you are assigning. Because of third fourth and fifth

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lines, you are assigning your values for your attributes

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or variables. Then immediately you're calling the respective

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object 'display_details' method.

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That's why you're going to get the same values in the output. That's it.

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You are assigning, and then you are displaying. That's

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it. So be clear.

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If you want to execute a method inside of a class, you have

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to write 'self.', but outside of a class

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you have to write your object name, '.', that method name.

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[no audio]

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That's fine. And if you observe this entire program, you are having

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these are like attributes.

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[no audio]

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Right. And these attributes, these attributes are specific for

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particular object because we are writing 'self.'. 'self' is

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nothing but object name.

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So these attributes are related to your object.

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That's fine. Now,

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I have a small requirement. After creation of, after creation

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of your objects.

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I need to find at last how many employee objects have been

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created using this template.

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[no audio]

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How many employee objects have been created by using this

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template. I have to know that. Count

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I need to find out. See what I am doing is,

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I am writing 'count'. 'count =', initially 0.

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[no audio]

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So whenever if I create 'emp1', at that time I need

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to increase this value, I need to increase this value.

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This value is not related with your object.

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This is related with your template, your class.

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This is class variable. See that. If I want to access that

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variable from outside of your class

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I need to access with the 'emp.count'.

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What is 'emp' here? Class name.

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0, you're getting. Let me comment.

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[no audio]

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By default we are calling 'display_details', right. Now

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just observe the output.

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[no audio]

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You're getting 0.

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Right. I can increase this value at any time, may be inside of a

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class, inside of a method, or outside of a class. See,

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I am doing 'emp.count = emp.count + 1'.

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So after that, I am printing my 'emp.count'.

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[no audio]

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That's it.

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Now this variable, if you define any variable outside of your

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methods without 'self', then that is for your template or

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for your class attribute.

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That is a class attribute.

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Now, what I am doing is, I am taking the help of this variable

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and whenever if I create an object at that time I will increase this value.

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I can increase either inside of a class or inside of a method

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or outside of a class. See how I am going to do that.

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See whenever if I create these values.

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Right. That means you're creating an object, right?

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So in this I'm going to create one more method.

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You can create any method.

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I mean like 'increase_count', 'increase_

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count_for_employee', not for your object.

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[no audio]

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But method is we are writing inside of your class, right. See

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what I am doing is, simply I am writing 'emp'.

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this is the class name, then 'count = emp.count + 1'.

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Of course, you can also write your shortcut for your

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arithmetic operation. Then simply 'return None'. That's it.

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[no audio]

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See, but I need to manually run this,

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I mean I execute this method whenever if I create an object,

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so I mean after giving your 'name', 'age', and 'salary' for any employee,

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after that I need to call 'emp1.increase_count_for_emp()',

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then 'emp2.increase_count_for_emp()'.

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That's it. Now see the result.

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Yeah, let me print so that you can understand.

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[no audio]

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So what is the variable? 'emp.count'. See the result.

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Two variables have been, sorry two objects have been created

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by using this template.

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Try to understand this variable, normal variable, right, like

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'x =', something. 'count = 0'. Now, if you define

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the variable immediately after writing your class, class name,

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if you define any variable, right, that variable is related

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for your class.

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So this is called class attribute.

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So why we need class attribute means, how many, suppose

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one of the example I am giving

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but you can define any number of variables based

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on your requirement.

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The very simple thing I am giving is, from the template how many

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objects has been created?

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To count that I am defining one variable, one attribute called

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'count'. That's it.

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So if you don't want to call externally your increase count

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for employee just comment these two methods here.

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So whenever if you create your variables immediately call

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'self.increase_count_for_emp'.

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That's it. Now see the result. Same output, right. 2, you're getting.

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Okay. So guys, this is all about simply class and object attributes.

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Be clear. These are class object attributes, and this is for your class

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attribute. And remember that class attributes we have to call

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or we have to save like 'self.', your variable name. Even

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while displaying that we have to take 'self.'. That is only

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inside of a class.

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But if you come outside, then you have to take instead of

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'self', particular object name, 'emp1.name', 'emp2.name',

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something like that. But for class variable, this

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is class variable or class attribute, 'count'.

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So either inside of a method, inside of a class, or outside

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of a class, you can always access with the help of 'emp',

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I mean template, class name, '.', your attribute.

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Be clear. For 'emp' object inside 'self', outside 'emp1',

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or 'emp2', outside, inside 'self.'. But whereas

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for class variables, attributes wherever you go, I mean

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in any line in your program, you have to take always 'emp.count',

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I mean your class name, '.', that variable. That's it.

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Okay. Okay guys, thank you for watching this simple video.

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[no audio]