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Welcome to Object Oriented Programming.

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First things first, let's make a little mental note that

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most things in Python are considered objects, even files.

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We've actually seen this before when we have a string, and

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we can, I did one too far there,

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we have a string with a dot and then hit tab, and

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we have all these different things that we can do with it.

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And even as an example, we can do 'name = "Python"',

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and let's do 'print(name)',

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and then let's also 'print(type(name))',

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and you can see that it's a class.

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Anytime you see class, just think object.

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So what Object Oriented Programming does, or OOP, is it lets

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programmers create their own objects and have their own methods

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and attributes.

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So a lot like we have 'name.upper', we can create that.

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We can create this '.upper', and it looks a lot like a function,

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actually. And the reason for that is because behind the scenes,

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it is a function.

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It's just already pre associated with a particular object.

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So moving forward, whenever you see a function inside of

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a class, which we'll dive into shortly,

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but whenever you see a function inside of a class, we call

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that a method. So this is a method.

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And this way of calling a function, it's just called a function.

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Objects or classes can also have properties or attributes,

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and that's really just saying that there is an internal type of variable.

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Now, that variable itself could also be an object and likely will be.

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But the idea is that whenever you have an object, and you

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have some sort of internal variable, a property or an attribute,

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and you have a method, that method can easily access that

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internal variable.

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You don't have to worry about scope or assigning a variable

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or anything like that.

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It's already inside of that class or inside of that object.

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And so it's going to have instant access to it already.

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So basically, what OOP does, is it allows you to create your

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own methods, create your own internal variables, create a

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class, and just like how we have string or int or tuple, it

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allows us to create our own objects just like that.

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And so basically, we can extend Python to do anything we wanted to do.

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We don't just have to stick with just strings.

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We can create a new type of object called a person, or a pet,

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or a hobby, or anything really.

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Now, why would we ever do this?

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Well, because in Python, they already give us methods like

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this, and that's because we are likely to use these on pretty

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much any string.

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It's a very common thing,

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so they provide it for us.

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We would essentially do the same thing.

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So we could have, for example, a person.

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Now, for the most part, people are born with two legs and

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two arms and a head.

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But people are also different.

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We have different features, like different hair color, different

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shoe size, things like that.

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And Object Oriented Programming lets us create repeatable

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and organized code without actually having to write the same

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10 variables about a person over and over and over again.

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And so sort of how we created a dictionary a long time ago

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where we had 'person', 'name = "Kalob"', we would have

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pre-defined things like arms,

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I've got two arms, legs, two legs, head, one head, something like that.

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And those are sort of actually terrible examples,

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but I think you get the point here where I have a 'person',

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and I could create another person with pretty much the exact

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same attributes and then just change, like, the 'name'.

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And so that's really just setting up a template so that you

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can create multiple people.

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You can create an army of people that all have, for instance,

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a default of 2 arms, or 3 arms, or 8 arms, 5 legs, and 2 heads;

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and you could copy that over and over and over again with

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a single line of code.

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You just have to set the rules for that template.

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That's what Object Oriented Programming is.

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So now a lot of people at this point in time, they think,

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"Well, why would I ever want to use Object Oriented Programming

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when I can just use variables and functions?"

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And that is the key question here.

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So functions are really nice for small pieces of code.

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You know, typically, a function does just one thing.

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It should actually only really do just one thing.

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But functions by themselves aren't organized well enough

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in code, and sometimes they need to be used together.

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So essentially, what Object Oriented Programming does is

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it allows us to group our functions and our variables together

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so that we know that they're all supposed to work together.

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And inside of our object, it sort of has its own version

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of scope, is a way to think about that, at least.

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And once you have an internal variable inside of one of your

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objects, or one of your classes, you can access it from pretty

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much any other method, or a function inside of your object.

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So again, we're really just grouping things together here.

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So if my 'person' dictionary here also had a function, and it

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needed to be 'say_hello', or this needs to be basically some

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sort of function that basically just says, 'print("Hello")',

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and this gets a little bit harder with a dictionary.

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With Object Oriented Programming, we can do that.

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We can say, 'person.say_hello', just like 'name.upper',

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and it will print out "Hello" for us, or anything else we wanted

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to. So let's go ahead, and I'm going to stop talking about

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the theory, and let's actually look at some of the syntax

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here. So to create a new object in Python, we use the keyword

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'class', and then we just give it a name.

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Now, typically, in Python, variables have lowercase letters

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and use underscores to separate them.

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So a variable name like 'my_name = "Kalob"', lowercase,

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lowercase, underscore, lowercase, lowercase, lowercase.

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In an object, we tend to use a different naming convention.

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Now you don't have to follow this rule, but it is a good

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practice to follow this rule.

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So it starts with the keyword 'class', and it just has upper case

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or camel case

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rather, camel case naming, like this, 'MyClassName', and then

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':', and then inside of here we have functions, and these look exactly

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like regular functions.

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So 'def say_hello(): print("Hello")'.

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Now the only difference here is because this is in a class,

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every single method that you write takes 'self' as its first

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parameter every single time.

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So let's go ahead and execute this,

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and let's, I don't know, call this 'person', I guess,

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and instantiate this with 'MyClassName()'.

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[no audio]

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And now we can do 'type(person)', and we're going to see that

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this is 'MyClassName' type.

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And if I do 'person.', and then hit, 'Enter', or not 'Enter',

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if I hit 'Tab', it automatically fills with the only option

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that there is, which says, 'say_hello', and I can just run

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this with parentheses.

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Now you don't need to specify 'self' in here.

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You don't need to say this. That's already in there, and Python

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will ignore it by default.

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It's basically just passing in the rest of the class data

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into here, so we have access to it.

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We'll dive into that in just a second.

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But now I can say, 'person.say_hello'.

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And this looks a lot like the same syntax as 'name.upper',

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'name.upper', 'person.say_hello'.

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Now a class can also take default parameters in here.

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And this takes a function, a magic function called

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'__init__()'. Because it's a function

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inside of a class, or in this case, it's actually called a method,

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it's going to take 'self' all the time,

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we never pass in 'self',

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Python does that for us.

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Then we could say the default 'name' is going to be "Person",

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and the default 'hobby' is going to be "Coding".

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And this again is pretty much the exact same as a regular

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function. Now at this point in time, we can say, 'print(name)',

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'print(hobby)'. And let's run that.

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And let's add this in here.

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We'll just run that once more.

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Now, because this was initially instantiated like this, the

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default 'name' was "Person",

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default 'hobby' was "Coding",

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it said, "Person", and "Coding", but we could actually change this.

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We could say the 'name = "Henry", and his default

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'hobby = "Being adorbs"'.

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He's super adorable.

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And we can see that that changes in here.

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That's not going to change.

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That's not going to change.

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But now, because we have this little variable in here, we

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might actually want to access that.

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So ideally we would just say 'person.name', just like a

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regular attribute on a string, for instance.

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But this isn't necessarily going to work yet.

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And the reason for that is because, "AttributeError:

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'MyClassName' object has no attribute 'name'."

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So this attribute here, even though we set it when we initially

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created this object, it says it doesn't exist, and that's

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because of scoping.

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That's why we learned about scoping.

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'name' is a scoped variable, only exists in here, does not exist

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anywhere else, cannot exist anywhere else.

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Not yet anyways.

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So what we can say is 'self.name = name',

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'self.hobby = hobby'.

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And now you notice how we are using 'self' here.

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What we're saying is, 'MyClassName

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.name =', whatever this is going to be.

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So by default, it will be "Person",

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but we're saying it's going to be "Henry". And we can create

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a new function in here.

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'def get_name(self)',

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and that 'self' is really just it's attaching itself to the rest of this class.

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So without it, it doesn't know about 'self'.

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It doesn't know about 'self.name', or 'self.hobby'.

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But we can say 'print(self.name)' now.

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And as a better example, let's go ahead and run this with

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'name'. Let's comment this out as if that never happened.

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'name' is set as "Person".

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It's printed out immediately.

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And when we run 'get_name', do we actually get that 'name'?

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We're going to see that this is a scoping issue here.

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So let's go ahead and save this.

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We'll rerun that, rerun that, that,

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and in here we could say 'person.get_name', is what I called

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it, right? 'get_name'.

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[no audio]

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Oh, and it's Python.

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Now, the reason I did that, very interesting,

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I probably should have used a different variable name.

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But scoping again. Scoping, looked for a 'name' in here, didn't exist,

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looked for a name in the object, doesn't exist,

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looks for a name in the global scope, which is up here,

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and that was "Python".

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So let's go ahead and 'del name' from our script here.

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So we're just going to delete that variable entirely,

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rerun these.

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[no audio]

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and now we get a "NameError:", it says "'name' is not defined".

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It says the variable does not exist.

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And that's because in here it technically doesn't.

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What we are looking for is 'self.name'.

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Now that doesn't exist because we haven't set it yet.

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'self' is a special keyword that refers to the object itself.

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So whatever this object is called, that's what 'self' refers

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to. Just like, "My name is Kalob", when I refer to 'myself', 'myself'

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is "Kalob", in this case, 'self' is 'MyClassName'.

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We'll, uncomment that one as well.

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And let's rerun these.

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And now we're going to see that 'self = 'name', and

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we can access that because 'self' is always passed in automatically

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in an object. 'print(self.name)' is going to be "Henry".

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[no audio]

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So let's rerun all these.

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'get_name'. There it is.

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"Henry". So that is a crash course into Object Oriented Programming.

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There's a lot of different things we can do with this.

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But really, all we did was we bundled a couple of functions

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together, 'say_hello', and 'get_name',

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and we made a couple variables accessible only inside of this class.

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We can also do 'person.name' now, and we can see that it's

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"Henry". 'person.hobby' is also "Being adorbs".

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[no audio]

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And so by grouping all of this together, we're getting the

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power of a dictionary,

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but we're also getting the power of functions, and scope is

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actually going to start working in our favor now.

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So this was a crash course into Object Oriented Programming.

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By no means do you need to understand all of us.

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We are going to go through a lot more examples of Object

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Oriented Programming in the coming videos.

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