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Hello guys.

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So we are going to continue the discussion with respect to Python.

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And we are going to continue the object oriented programming series.

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And in this video we are going to discuss about polymorphism.

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Now polymorphism is a core concept in object oriented programming that allows object of different class

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to be treated as objects of a common superclass.

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I know there will be a lot of confusion when you read this sentence.

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Uh, but just go ahead and read the next line.

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And if you are not even understanding over here, don't worry, I will show you a lot of practical example

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which will actually help you to understand each and everything.

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So it provides you a way to perform a single action in different forms.

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Okay.

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Poly form ism basically means multiple form okay.

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If you split this word it is basically called as multiple form okay.

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And here it is written polymorphism is typically achieved through method overriding and interfaces.

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So let me just go in and talk about this, and let me just give you a good example to make you understand,

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okay.

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But it is my duty to probably write this kind of definition so that you also know the definition with

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respect to this.

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Okay.

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Now what does method overriding allows a child class.

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So here I'm just going to give you this command C or let me make this or remove this completely.

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And and let me make or add a markdown over here.

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So here you can see let me just go ahead and execute this method.

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Overriding allows the child class to provide a specific implementation of a method that is already defined

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in the parent class.

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Okay.

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That basically means let's say if I'm defining a parent class, okay.

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Over there I have defined a method, right?

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Uh, let's say the method will be like, uh, if I probably create a dog class, the method is speak.

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Okay, so one dog, uh, makes a sound.

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Woof woof woof.

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Then let's say that I'm inheriting that particular dog with some child class.

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Now, that particular dog makes a louder sound.

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Woof woof woof woof woof.

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So there what we are doing, we are overriding the functionality of that particular method.

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Right.

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So method overriding is nothing, but it allows a child class to provide a specific implementation of

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a method that is already defined in its parent class.

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So let me just go ahead and take one specific example.

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And here you'll be able to understand.

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So first of all I will go ahead and create my base class okay.

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Now this base class will be my animal class okay.

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So let's say that this is my animal class.

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And I'm going to just going to create a function that is called as speak.

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And here I have not written any constructor because I'm not defining any attributes.

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Okay.

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So let's say that I've used speak and with the self parameter and it is just going to return something

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like the sound sound of the animal okay.

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Something like this.

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Now this becomes my base class.

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Now let me just go ahead and derive my derive class okay.

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Or write down my derive class one.

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Now in this derive derived class, let's say I will go ahead and derive or I'll create a child class

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which is called as dog and it is basically inheriting from animal.

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Okay.

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And then we go ahead and define the definition definition speak.

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And here we go ahead and define self.

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Right now.

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See the method is same over here.

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Right.

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If we are inheriting this particular class, you will be able to see that.

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Okay, fine.

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This is the method that I have right over here.

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And I can also go ahead and return my own definition.

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So let's say the dog makes a sound like woof.

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Okay, so this is the sound that the dog makes.

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So what I have actually done the same method is there but different implementation.

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So here method overriding allows a child class to provide a specific implementation of a method that

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is already defined in the parent class, so this method is already present over there, but the child

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class has provided its own specific definition or implementation right now, let me just go ahead and

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create another derived class okay, derived class.

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And this time I will go ahead and create a class that is called as Cat and let this get inherited with

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animal.

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Okay animal.

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Now here I can again go ahead and override the functionality of this method.

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And here I can say, hey, it returns meow.

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Okay.

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It returns meow.

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Now let's go ahead and define our or create our object.

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So here what I'm actually going to do I will just go ahead and write dog is equal to dog.

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Okay.

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Now if I go ahead and print dog dot speak now which method it is going to just call, it is just going

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to make sure that it calls this specific method.

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Right.

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And similarly, let's say that I go ahead and create my cat okay.

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And let's say that here I will just go ahead and print cat dot speak okay.

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Now if I go ahead and execute this here, you'll be able to see that hey I am getting when I go ahead

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and execute dog dot speak, I'm actually getting woof when I'm uh, executing cat dot speak.

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I'm getting meow.

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And this is what Mr. Method overriding is all about.

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You know, the same method is getting overridden in the derived class with its own implementation.

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Right.

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And, uh, I can also do one thing.

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Okay.

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Uh, after doing all these things, you know, I can also create one additional function.

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So function that demonstrates.

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Demonstrates polymorphism.

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Here, what I will do.

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I'll go ahead and create a function.

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And this is a public function, not inside a class okay.

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Not inside any class.

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So let's say that I'm going to create animal speak.

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And here we will provide an attribute of the class or object of the class okay.

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And then we can just go ahead and write print animal dot speak method.

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Okay.

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Now this animal that I am actually providing, it's an object object of this specific classes.

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Now after defining this method I can just go ahead and write print okay.

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And I can go ahead and say dog dot speak or let me just go ahead and uh, sorry, it should be animal

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underscore speak.

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And here I will just be providing dog once.

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I probably define this and execute it.

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Here you can see that I'm getting hoof right because as soon as I call this function here, we are giving

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the object of this particular class.

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And inside the same dot speak method is basically getting called right.

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So this way also you can probably show polymorphism.

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But here what we have done, we have done method overriding.

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We have we are just overridden all the functions over here from the base class till the child class.

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Okay.

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So this was one example over here.

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Now let me just show you one more, another way where I will be showing you polymorphism with functions

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and methods.

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Functions and methods okay.

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Now polymorphism can be also implemented using function and methods to process objects of different

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types in the same way.

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Right?

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So here let me just go ahead and show you one base class.

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Let me just go ahead and create one base class here.

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The class will name will be shape.

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Let's say that I'm going to define shape.

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Now let me just go ahead and write definition area.

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So I'm going to create a function which is called as area.

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And here I'm going to give my self keyword okay self Self keyword.

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Now let's go ahead and return the area of the area of the figure.

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Okay I'm just going to probably give a print message.

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And this is basically present in the base class okay.

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Now what I will do I will go ahead and create my derived class.

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Now see this okay.

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Again I here I'll also be implementing function overriding okay.

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So this will be my derived class one okay.

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Let's say that I'm going to probably create a rectangle rectangle.

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And you know rectangle will inherit shape okay.

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And you know if for rectangle definitely what we require in order to calculate the area, it is nothing

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but width and height.

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So I'm just going to create my init method.

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And here I'm going to give self comma width comma height.

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This is what I'm going to pass in the runtime.

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I will go inside this.

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Now let me just go ahead and create my parameters or attributes.

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That is nothing but self dot width.

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Self dot height.

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And then we'll go to the next sentence.

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Oh sorry.

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This should be assigned to width.

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Okay.

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Then we will go ahead with self dot height which will be my another attribute.

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And this I will assign it to my height okay.

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Now I will go ahead and call this area function.

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Right.

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Now here what I am doing I am again I'm overriding this area method because the functionality will be

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little bit different over here.

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Right.

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How to calculate a area of a rectangle.

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It is nothing but just return self dot width.

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Self dot width.

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multiplied by self dot height.

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Self dot height.

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Right.

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This is what we are specifically doing.

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Now let me just go ahead and call the derived class two.

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Okay so here we have completely redefined or we have overridden the entire function.

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Right.

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So it's like all the function are basically having multiple forms as we keep on, uh, making sure that

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once our derived class inherits the parent class, we are basically redefining this entire function

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or we are overriding the functionality.

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Okay.

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Now let me just go ahead and create another derived class.

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And this time I'm going to create it as circle.

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Okay.

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This will again inherit shape okay.

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Shape.

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So let me just go ahead and inherit shape.

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And now this time, you know, I'll be using an init function and this will be a constructor.

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And here what I require in order to calculate the in order to calculate the area of a circle I just

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require radius.

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Right.

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So here I'm basically going to write self comma radius okay.

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Now let me just go ahead and write self dot radius is equal to radius right.

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So here you will be able to see that I have able to just get this particular parameter.

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I am able to create it now here also the area definition will be the function will be different right.

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So how do I calculate the area over here.

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I will just say return right.

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It is nothing but pi r square right?

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Pi is nothing but 3.14 multiplied by the radius into sorry self dot radius self dot radius multiplied

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by self dot radius pi r square.

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Right.

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Done.

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And this will basically give me the area.

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Now what I will do along with this, I will just go ahead and write a function that demonstrates polymorphism.

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And here is what I will be writing.

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So here let me just go ahead and write print underscore area.

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And here I'm actually going to give me give the shape which will be an object okay of a specific class.

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And we will just go ahead and print with my f string.

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The area is nothing but shape dot area.

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Right shape dot area.

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Which will be my function.

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Okay.

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Now this is what we are going to just print it.

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Right.

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Now let me just go ahead and create the objects.

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So first of all what I'm actually going to do I'm going to create a rectangle object.

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Go ahead and use rectangle right.

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Basically use four comma five.

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In case of circle I just need to provide my radius.

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So let me just go ahead and define circle with radius.

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Radius is let's say three.

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Now if I want to go ahead and just call the area function I will just go ahead and write print underscore

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area.

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And I will give the object that is rectangle.

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Okay rectangle.

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And similarly I will go ahead and call print underscore area where I will be giving circle right.

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And this is how we execute it.

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And here you can see the area okay.

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The area is 20 and 28.25.

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So this is the area with respect to uh, you know uh the, the, the, the, the area of the rectangle

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which we basically write length into breadth.

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So nothing but four into five.

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And if I go ahead and calculate pi r square.

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So I'm actually going to get 28.25.

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Right.

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So this is one amazing example.

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And here you can see that we have used functions.

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We have defined another function that demonstrates polymorphism over here.

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And uh this is one of the amazing example with respect to this okay.

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And here also we are basically playing with the same method name but with different different definition.

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Okay.

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Now let me just, uh, introduce you to see, uh, I've already written over here something like this.

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Right.

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Um, polymorphism is typically achieved through method overriding and interfaces.

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Now let's talk about this.

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Interfaces.

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What is interfaces in other programming languages we basically say interfaces in Python.

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We say it as abstract base class.

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Now what exactly it is.

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Let's discuss about it.

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So polymorphism with abstract base classes Okay.

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Now abstract base class.

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Uh, if I really want to define it.

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Okay.

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It's very simple.

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Let's go ahead and see the definition.

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I'll paste it over here.

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And let me just go ahead and write this okay.

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Uh, important topic altogether.

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Okay.

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Abstract base class are used to define common methods for a group of related objects.

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They can enforce that derived class, implement a particular method promoting consistency across the

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different implementation.

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Okay, so abstract base class.

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That is the reason we say it as ABC.

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Okay let's do one thing okay.

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Let's let's show you an example over here.

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Uh I will be defining two important things.

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First I will write from ABC.

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Okay.

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Now what is this ABC?

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We are basically using abstract base class.

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We are going to import ABC.

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Okay.

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Along with that we will be importing abstract method okay.

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This abstract method is a kind of decorator okay I'll be talking about what exactly is decorator as

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we go ahead.

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Right.

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But just consider right now this is what, uh, abstract class is all about.

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You know, it is it is just like it is just used to define a common methods.

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Okay.

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So I will just go ahead and define an abstract class.

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How do I define an abstract class.

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This is what I'm going to show you.

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Abstract class okay.

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Now um abstract class here I'll say hey, uh, let's create a class called as vehicle.

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Okay.

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And this I'm going to inherit to the abstract class, which will be like an empty class itself.

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Right?

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So, uh.

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this abstract class, afterwards, I define it, I will be defining abstract method.

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Also see, in order to just give you a simple definition of abstract class, it is like a complete empty

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class.

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You know, there, uh, if you are defining also method, it will be initially empty.

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Okay.

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So that is the reason why we have written that abstract base classes are used to define common methods

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for a group of related objects.

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Here no definition will be there much.

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Okay.

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So, uh, with respect to this, uh, now I have created this particular class.

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I'm not putting any information, but let me just go ahead and create an abstract method.

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Okay?

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Abstract method is just like an empty method, but it is kind of common class.

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That is probably going to happen in each and every class, because we are going to inherit this kind

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of abstract class onto this.

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Right.

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So here what I'm going to write, I'll just go ahead and write define start engine.

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So this will basically be my function.

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And here I'm going to use my self keyword.

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And since it is abstract it needs to be empty.

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So I am going to just write pass okay.

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So this is how I have actually created my abstract class.

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Along with that I am also creating my abstract method called as Start Engine.

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Now what I will do for my derived class one I will inherit this.

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Okay, so let me just take class car And here I'm just going to use vehicle okay.

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Now you know that I have defined my abstract method which is completely empty.

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Now I can since I'm inheriting vehicle, I'll also be inheriting this particular method and I can define

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my own function.

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So that is the reason we'll go ahead and write definition start underscore engine okay.

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Start underscore engine self.

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And we are just going to return over here Car engine started okay.

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Some information.

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Car engine started.

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Okay.

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And here you can define your own init method also inside this particular class also.

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Right.

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Define any number of parameters that you want okay.

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Now uh similarly if I go ahead and create my derived class two, you'll be seeing hey, let's go ahead

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and create this particular class called as Motor cycle.

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Okay.

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And here I'm actually going to give my vehicle okay vehicle class.

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And let's go ahead and inherit it.

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And uh if I go ahead and write definition start underscore engine here I'm just going to return motorcycle

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dot sorry motorcycle engine started.

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So here you can see this function is having a different definition inside motor class motorcycle class.

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And it has a different definition inside the child class.

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Okay then uh let me just go ahead and create the object of the class.

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So create objects of car and motorcycle.

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Now see I will just go ahead and create it.

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Okay.

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And we can do the same implementation like this also.

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Right.

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So I have inherited over here.

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Let me just go ahead and define one function that will demonstrate my entire polymorphism.

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And now I can just go ahead and start this vehicle and just let me define my car.

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And if I go ahead and execute it, you can see that automatically it is being able to call this called

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as uh, start engine.

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And here we are able to display it.

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So here I have actually shown you polymorphism with the help of method overriding.

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Along with that we have also seen with the help of abstract class.

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So this two you definitely need to know.

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And uh, again uh, ending this session I will try to provide some conclusion which is a good habit.

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Okay.

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So here with respect to the conclusion, you should know why polymorphism is important.

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It is a powerful feature that allows the flexibility and integration in code design.

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It enables a single function to handle objects a different class, each with its own implementation

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of a method.

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By understanding applying polymorphism, you can create extensible and maintainable object oriented

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programs.

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Okay, but here we are just seeing that what all features it has with respect to polymorphism.

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Right.

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So yes this was it for my side.

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I hope you like this particular video.

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I'll see you all in the next video.

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Thank you.

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Take care.