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Hello, and welcome to Object Oriented Programming with your

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host, Kalob Taulien

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In this lesson, we're going to be talking about class methods.

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Now, a method is honestly, it's just a function inside of a class.

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That's literally all it is.

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But because it comes with a few extra goodies, like being

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able to access the 'self' keyword, it is slightly different

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than a regular function,

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and so we call it a method.

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So I'm going to create a sample class here called 'MyClass'.

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It's going to have an attribute,

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a default attribute, 'course = "Python for Everybody",

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and 'def __init__(self)'

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I'm not going to use that, not just yet.

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So technically, I didn't need to write that,

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but because I did, I put 'pass' in there to basically tell

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Python, "Hey, I know it's there.

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There's nothing in there.

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Just let it be".

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And then I'm going to create another method in here, and

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this is going to be a completely custom one.

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And this is just going to be called 'thing'.

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And so its first parameter is going to be 'self'.

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First parameter is always going to be 'self', and that's what

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connects it to this entire class.

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And then it can take an optional parameter, if you want to

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give it a parameter.

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So I'm going to call this 'param1', and by default it's going

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to have a regular value of "Thing", and all this is going to

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do is 'print(thing)'.

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That's all it's going to do.

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So if you look at this, objectively speaking, this looks

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exactly like a function.

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The only difference is we have to put in 'self'.

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So let's go ahead and run this.

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And if you were screaming at your screen saying, "Hey, Kalob,

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that's almost like a function,

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except you missed a thing.

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Yep, I did. I missed the colon.

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So let's go ahead and run that.

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And let's just instantiate this in a variable.

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'my_class = MyClass()'.

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So we actually run the class.

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Nothing happens.

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It looks like nothing happens.

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But if we do 'my_class.thing', well, this is actually looking

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for a 'param1', but by default, it's already going to be "Thing".

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So it's going to 'print(thing)' in here,

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and I actually did that wrong.

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That's not supposed to be 'thing'.

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I was looking at that while typing the wrong thing.

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So let's rerun these.

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There we go. It says "Thing".

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But if I said 'my_class.thing("Something else")', and I overwrote

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that parameter, it's going to overwrite the variable inside

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of the method, inside of the function.

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Now, where '__init__' comes into play, is we want to set a different

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parameter in here.

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So let's add the number of students in this class.

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And so we're going to say, 'self.students = students'.

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And if we create another method in here, 'def get_total_students',

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pass in 'self',

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we can 'print(self.students)'.

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And so what this is doing, is saying when you create this

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new class, put in the number of students.

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So let's put 100_000.

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And so this parameter is going to go into the 'students' variable

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here, it's then going to be reassigned to 'self.students',

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which is the same as saying 'students = 100_000'.

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And because this is an attribute, it's a variable inside

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of this particular class,

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we have access to 'self.students' in here, and you can actually

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see that it just makes that quick connection between

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'self.students' here and 'self.students' here.

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Just get rid of this one because we don't need that.

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And when I run this

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[no audio]

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'Thing', still works.

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That still works.

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And if I do 'my_class.get_total_students',

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this is going to print out the total number of students. Cool.

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And in fact, a better example of this would be using

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an f-string. We could say, 'f"The total students is ", we can put this

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as a variable.

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Let's save that. Rerun these.

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And now it says, "The total student is: 100000".

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Now the reason I did that, is because we can also now use

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'self.students' from 'MyClass', or the variable.

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So now we're jumping around from point to point.

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We're really referencing a lot here, but we can now easily

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say 'my_class.',

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what was that variable name? Just 'students'.

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[no audio]

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And that gives me just a 100000, because that's

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what I put up here.

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So whenever you are using methods or functions inside of a

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class, it looks exactly like a function.

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So 'def', your function name, always take 'self',

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and that's what's going to connect it to the rest of the

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class, that gives it access to run 'self.thing'

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if we wanted to, or get 'self.course', or 'self.students', that's

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what connects it to this class.

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And then parameter.

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If we wanted to work with a parameter, we could force it

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to be in there, and then just do something in here, any sort

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of logic, it could print something, it could return something,

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it could even change 'students'.

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And actually, in fact, now that I think about it, that is a very good idea.

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Let's go ahead, and update this with 'def add_student'.

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It always takes 'self'.

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And we're going to say 'self.students = self.students + 1'.

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And let's print this out as, "New total is : ".

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[no audio]

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Let's run that, run that, run that, run

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that, just rerunning all my old cells here.

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'total_students', we're currently at 100000.

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But if we do 'my_class.', and then hit 'Tab', we can see

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we can add a student, 'add_student' in here.

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That's a method,

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so it takes parentheses.

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And again, it does not need to have 'self' in there.

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'self' only references that part, the class itself,

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and Python magically does that for us behind the scenes.

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So run 'my_class.add_student', and we could run this over and

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over and over again.

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And this will continue to add the number of students for us.

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And then, if we just wanted to double check, we could do

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'my_class.students',

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and this is going to show us 100006 students, just like that.

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[no audio]