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Hey, welcome to the last video for today.

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Here you're going to learn about abstract classes and abstract methods.

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Yesterday, you do remember that I introduced you to a class such as Digital ticket.

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Which you'd inherit from reservation ticket.

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Yesterday we simply wrote this in a Python console just to refresh your memory.

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So it was basically something like this.

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And then I showed you that you could overwrite an existing methods of.

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The parent class.

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So generate is a method to all that parent.

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And here you could return something else which is different from that.

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So let's say hello, this is your digital ticket.

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Just an example.

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And you could, of course have more methods such as download.

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And have some codes here and so on.

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No, this is not the best practice, actually.

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A better way to do this would be to create something known as an abstract class from which other normal

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classes inherits.

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So this class would inherit from that abstract class, which we will create now.

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And the digital digital ticket class would also inherit from that class.

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So let's create that abstract class here.

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This would have a name such as Ticket in this case.

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And this would have the method generate.

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And it would have pass as code.

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And then the other classes such as reservation ticket would inherit from the ticket class.

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And same goes for digital ticket ticket.

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Now we need to add something else to the abstract class to actually make it an abstract class.

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And I'll explain you why we call this an abstract class.

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What we need to add here is a parent for this class, and the parent is ABC.

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What is ABC?

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ABC is a class which we need to import from.

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A, B, C.

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This is a module, a standard module in Python.

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You import a, b, c, A, b, C stands for Abstract Base class.

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Same goes for this A, b, c, So that's a module.

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And that's the class.

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So b c goes here.

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So now this is a child of an abstract class.

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And then in here we add the abstract methods decorator, which also should be imported from ABC import,

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ABC comma, abstract method.

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So that should be the same as this here.

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Now, what's special about this class is that if you let me try to show you that to you in the Python

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console.

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So let's import that and then let's define this class or you can import it, but I'll just copy and

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paste it here.

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And then if I try to create an instance out of a ticket class, this class, right, I am instantiating

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it.

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If you try to create an instance, you will get an error.

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The error is very specific.

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It says can't instantiate abstract class ticket with abstract method generate.

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So you can not instantiate an abstract class because an abstract class is an abstract class.

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So it's a class which is not supposed to create instances is something abstract, and its role is to

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define a structure.

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Basically.

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It's not a must to use abstract abstract classes, but it makes your code more clear.

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So you see, for example, now that, oh, this reservation tickets inherits from this ticket class.

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Oh, so you say, let's see what what the ticket class is and you see here, then you see that this

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has this generate method.

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And then you realize that every child inheriting from that class should implement a generate method.

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So that's a must now.

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So that way you basically are trying to define some rules.

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Perhaps you are collaborating with other programmers.

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So that makes it very clear that all the ticket classes, including this one in here, which also is

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inheriting from that abstract class, this also should have a generate method.

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So this way you are forcing the programmers, which could be you or another collaborator to create to

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implement a generate method for each class, because that is a must if the programmer doesn't implement

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a methods.

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For example, let's try to create a PDF ticket here which inherits from the ticket abstract class,

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and this has a generate PDF methods.

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Let's pass for now and it doesn't have a generate method.

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In that case, when you try to instantiate PDF ticket you're going to get an error.

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So this will not work and that means it will force the programmer to actually remind themselves that

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they need to add a generate method.

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So it's good to use abstract classes when you see that it's a must that all those classes should have

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a particular method.

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That was about abstract classes and abstract methods such as this one in here.

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Yet with that you have a very complete overview of classes and advanced concepts of both classes.

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As we move through the course, we'll have more real world scenarios when we use classes.

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So basically most of the apps will be building from now on.

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We'll have an object oriented programming structure using classes.

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That's why I introduced you to object oriented programming during these last few days, so that now

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you're prepared to actually practice classes in more real world scenarios.

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So thanks a lot for following so far.

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And please go to the next day and I'll see you there with building some more programs.

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Thanks.