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Welcome back everyone to this lecture on object oriented programming.

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Object Oriented Programming or opii allows programmers to create their own objects that have methods

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and attributes.

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Recall that after the finding a string list dictionary or any other built in object with python we actually

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have the ability it's called methods off of them using that method name syntax.

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For example if you define the string you're able to call upper off that string to make uppercase Orphy

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had a list you're able to call a pen to add something to that list these methods actis functions that

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use information about the object as well as the object itself to return results or to just effects them

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for a change on the current object.

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For example like I just said that would include appending something to a list or counting the occurrences

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of an element in a tuple O.P. allows users to create their own objects.

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The general format is often pretty confusing when you first encounter it and its usefulness may not

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be completely clear at first.

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In general opii allows us to create code that is repeatable and organized and we really start diving

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into a flask.

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We're going to be using it quite a bit so it's important to have a solid foundation on it right now.

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So again for much larger scripts of Python code such as the ones we're going to be creating the flask

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functions by themselves aren't going to be enough for organization and repeatability commonly repeated

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tasks and objects should be defined of O.P. to create code that is more usable.

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So let's check out the syntax.

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So here you have the basic syntax for object oriented programming.

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Let's go over some of the keywords before hopping over to the text editor to explore some examples.

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So we start off with the keyword class and then we decide on the name of the class and notice here.

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Now I'm no longer following that snake casing of everything lowercase and underscores instead of classes

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the convention is Camel casing.

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Basically we have uppercase or capitalized letters and then every new word has a capitalized letter

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so we say a name of class that way later on your code you can easily distinguish between a function

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and a class.

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So once we defined our class we have this init method and this is going to allow us to initialize the

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actual class and notice here how it has a couple of keywords such as self and then Parama one and program

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to basically what this means is when you create an instance of the class you have the ability to create

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some attributes for the class themselves.

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So the pram to that you actually pass into the class gets sinked to the instance of the class itself

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and that actually uses that self keyword which is shown here.

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So basically you're going to pass and Parama to and then that's going to be assigned to that instances

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own attribute Parama to and this will make more sense as we actually code examples out in the text editor.

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The other common thing to see inside of class is a method call.

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And notice how this looks a lot like a function.

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It just happens to be inside of a class.

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And again it's using that sulpha keyword so using that self keyword.

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This is basically going to tell the class to perform some sort of action with information about itself

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and maybe some of its parameters.

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So in this case it's just asking it to print out one of its attributes or parameters.

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OK so we went over the basic syntax but it's not going to make a whole lot of sense until we actually

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get our hands dirty and start coding it out.

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So let's explore.

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Object Oriented Programming with more detail with some code.

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Laurie I want to begin this lesson by remembering about basic Python objects.

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For instance I could have a list one two 3 and then I could say my list and append something to the

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list.

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Second call this method off of this list object and in fact pretty much everything in Python is an object

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which you can test or check by using the type keyword.

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So I can say Type of my list and then we can print out the result of this so that I can actually see

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what type of object that is.

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So when I run this I get back that its class list and then maybe I'll put in some number there.

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So what type is 12 when I run this.

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It says it's class I.A. or class Integer and pretty much all your different objects are going to have

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some sort of type associated with them.

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So let's do twenty three point five.

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Save that.

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Run it.

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And this is class float.

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The main idea here is we're not going to be able to create our own class so Ill say class and then whatever

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class we created and then our classes are going to have their own methods that we can define.

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So let's try this out.

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We'll start off by using the class keyword and then you choose a class name that's capitalized.

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In our case we'll just call this sample and then you can either have a colon or open and close parentheses.

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Either will work fine open in the open and close.

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Prince is right now because later on we're going to need them to inherit from other classes.

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So we'll say class sample colon and then pass.

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Basically this class is totally empty.

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It doesn't do anything then I create an instance of the class.

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This is really similar to when we're doing something like creating an instance of a set object.

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So I'll say x is equal to sample.

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Open and close princes.

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Let's go ahead and check out the type of this object.

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So I'll say what is a type of x.

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And when I run this it says hey class main sample.

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And at the end of the section the course will talk about this main variable more that you can get the

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idea here that we've already been able to create our own ogic type in this case.

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It's a really simple object called a sample object.

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OK let's expand on this idea by starting to understand attributes for objects in order to do that.

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I'm going to create an entirely new class we're going to create a class or a dog object.

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So say class dog and then I'm going to use a special method and these special methods are often called

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Dunder methods because they have a double set of underscores surrounding them.

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So I will say underscore underscore I and I-T underscore underscore and then I'm going to passen the

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self parameter and then I'm going to pass on another argument for Breede.

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So I have a breed of dog.

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They'll say colon and we'll say self-taught breed is equal to breed.

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So let's break down what's actually happening here.

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We have this in method and this is automatically called right after you create an instance of this object.

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And then each attribute in the class definition begins for reference to the actual instance object.

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So by convention that's what this self keyword is basically saying we're saying that this particular

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instance of the object such as when we say something like x is equal to dog and this case will have

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to provide a breed such as lab or saying OK X that instance of the dog that breed is going to be whatever

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breed was passed then.

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In this case it's a lab.

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So let's actually see what happens here.

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In fact let's go ahead and then print out the type of x so will run this and we get back.

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We have a main dog type.

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What's interesting is now off of my doctype I'm going to be able to call breed off of it as an attribute.

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So when I read this it says that the type is a string which makes sense but if I just ask for Breit

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itself because lab was a string that's going to report back o the breed of the x variable instance of

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dog is lab because that's what you find here as the breed.

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So all you're doing here is when you call a dog an instance of dog you automatically call this initialization

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method and then you in whatever arguments or parameters.

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Essentially whatever attributes you want for the object and the system to self.

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And in this case it ends up being X..

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So X here self that's the connection.

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Now we say dots the attribute name is equal to whatever attribute was passed then.

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In this case it's lab.

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So this is basically saying Breede is equal to lab.

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So they're in this again Negat lab.

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Often what is confusing for beginners is the fact that we're using Breede here three times breed breed

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and self-taught breed just to make it really clear.

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I want to show you that you could also say this.

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I could say input breed

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input breed and then say this and put Breede is let's go ahead and make it like a husky or something.

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So what this is saying is when you create an instance of the doll class as I'm doing here a line 6 you're

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going to automatically call this init method.

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And then there you're going to use the self keyword to assign attributes.

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So you're going to say then self essentially becomes X here so X that breed is going to be whatever

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you passed in as the input breed.

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So you take the input breed and you assign it to self-taught breed which ends up being Huskey.

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So when you say Prince X-type breed and you run this you get Huskey.

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So notice how this works.

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Again you just passing in an input argument for an attribute and then you assign the input argument

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to the attribute name.

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Now by convention you usually have both the argument and the attribute share the same name which is

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then why you see something like breed breed and then breed.

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But I wanted to show you that aspect so you don't get confused by saying breed there three times.

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So pretty much all the attribute names are going to see them three times one for the argument one for

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the assignment and then one for the actual dot attribute call.

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OK so let's try adding in another attribute.

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So dog should have names so I'll say breed and name and then we'll say that this instance of the dog

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self-taught its name is going to be the name that's passed in so we'll save that and then let's provide.

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Now we have to change this back to breed.

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And in fact we totally don't need to actually say breed is equal to and said it could just say just

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pass and husky and then the name of this dog will have it be Sammy.

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Now let's have this variable now be called Sam so I can then ask for attributes of Sam I can say what

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is Sam that breed or Prince what is Sam dog name and that is here.

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Because these are attributes I don't have open and close princes.

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Those will be methods that we'll talk about later on

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looks for up to have the princes there run this and now I see Huskey and Samie.

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So I have this instance of a dog whose breed is husky and Sammy is going to be that dog's name.

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So those are the basics for attributes.

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Now there are also what are known as class object attributes.

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So we can say class object attributes.

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And these are attributes that are defined outside any methods of the class.

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So it's going to be outside these methods.

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And by convention they're the very first thing that comes in before in it the purpose of class object

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attributes are for things that are going to be true regardless of the instance of the dog.

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So for example we could say that the species of the dog is mammal.

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Now technically biologically it's not true.

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It's actually a different term it's called class for a mammal but I don't want to get confused with

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this keyword.

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So just say species.

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So if you have some familiar biology that's forgive me.

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But anyways we're going to say that all dogs regardless of their breed and regardless of their name

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they're always going to be mammals.

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So that's why I'm sending this attribute as a class object attribute and because it's a class object

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attribute and it's outside as in method.

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I actually don't need to use the self-taught keyword to zoom out just a little bit so we can see the

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whole picture here.

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So again I have this class dog I had this class object attribute.

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And when I defined the instance the dog had to provide a breed and the name.

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So if I were to say this and run it I won't see anything different.

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But now all I have access to that class object attribute which in this case we said whoops not animal

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is species.

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There we go.

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And then I'll report back mammal because it doesn't matter if I have a lab whose name is Franki as long

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as it's a dog species is always going to be a mammal.

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So any dog regardless of their breed or name will always have the same species attribute.

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So that's the purpose of a class object attribute it's an attribute you want to have permanently set

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beyond whatever the user of this class can provide.

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OK so that's going to be something that's always true regardless of the instance of the dog.

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So so far we've discussed the basics of the class syntax and the basics of attribute calls including

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this method in order to assign attributes to a new instance of the dog object as well as class object

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attributes which is going to be the same attribute regardless of whatever specific attributes were declared

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in the init method.

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Coming up next in part two we'll begin to discuss other methods you can add in to a class.

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We'll see if they're.