WEBVTT

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<v ->Hi guys and welcome back,</v>

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in this video we're going to learn about two methods,

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the str and the repr methods.

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In Python methods with two underscores on each side

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are special methods also called magic methods at times,

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because Python will call them for you in some situations.

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For example when you do person,

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Python calls the init method for you,

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even though you didn't say

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Python dot underscore, underscore init, you know.

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So that is why it is a magic method,

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you don't have to call it yourself,

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Python can do it for you at times.

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So let's create a person that I'm gonna call Bob here

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and he's gonna be 35.

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Here we're creating a person object by calling the class,

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then Python calls the underscore, underscore,

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init, underscore, underscore method.

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Gives us a new empty object that we're calling self,

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and then we're setting the name

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and the age properties of that object to be our parameters

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that are arguments here,

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so Bob and 35 will be stored in Bob's name and age.

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Now if we print Bob then you may see something

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a little bit weird, which is this.

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That's less than, underscore, underscore, main,

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underscore, underscore, dot, person,

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object, at, a bunch of numbers.

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Greater than.

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So what does this mean?

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What python is doing at this point is

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when you've told it to print Bob,

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Python is going to print out a string

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representing the Bob objects that we've created.

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And the reason why Python is printing out

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a representation of the object,

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is because you can't really print an object,

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you have to print a string, some characters

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and numbers and so on.

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So Python is saying that this string

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that it printed out is what it thinks represents our object,

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this is a default string, and all objects

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and all classes you create will look something like that,

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unless you change it yourself.

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So the purpose of printing out an object can be to fold.

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The first purpose can be to return

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a nice, easy to read string so that in your applications

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you can print out an object

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and your users can make use of that.

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For example if they wanted to know about this Bob person

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then potentially you could print out Bob

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and it could show them some nice information about Bob.

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The other reason to print out an object

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can be for programmers, you can print out an object

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so that you can see the objects information

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in case you want to recreate the object.

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Let's start off with the first option.

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We're going to modify Bob so that when we print him out

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we'll get some nice information

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that our users can make use of.

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The way we do that is we do def, underscore, underscore,

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str, underscore, underscore.

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Then of course the self parameter,

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and in we go to the Bobby.

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The underscore, underscore, str, underscore, underscore

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is a method, that is a magic method

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because it has the two underscores on each side,

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and this method gets called for you,

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when you want to turn your object into a string.

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Let me just return hello from here.

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Any now we're going to print Bob.

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Notice that we get hello out.

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Because what Python has done,

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is when you ask it to print an object,

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Python realises that really what you want

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is a string representation of that object since

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that's the only thing you can actually

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print out in a console.

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When you ask it to print an object it is going to

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turn that object into a string using the str method,

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and then it's going to print that.

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So instead of returning hello here,

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we could return something a bit nicer.

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Run about the goal, remember the goal

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when you're using the underscore, underscore,

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str, underscore, underscore method is to

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print out a nice, easy to read string for users.

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So we're going to print something like this,

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person, self, dot name, self dot age, years old.

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Now if we run this code again,

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you see that we get person Bob, 35 years old.

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You can remove the person if you'd like.

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So as well as the str method, you have another one

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called the repr method.

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The goal of the repr method is to be unambiguous,

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and if possible it should return a string

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that allows us to recreate the original object very easily.

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So I'm going to return person, self dot name, self dot age.

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Like that.

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Notice that I'm putting less than and greater than symbols

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that is just for looks, it is to tell programmers

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that read this string here

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that we are printing out an object.

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Now if we press play, you can see

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that the str methods output is still printed out.

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That is because by default when you print out an object

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Python assumes that you wanna show it to your users.

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You don't want to show the output of the repr method,

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you wanna show the output of the str method.

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The repr method is used in a few other places

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such as the Python debugger

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that we will learn about later on.

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But usually the str method is used

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so if you wanna make sure to test out your repr method,

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just comment this one out,

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put a couple of hash symbols in front of it

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and then press play.

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And then you see that you get person, Bob, 35.

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And if you really wanted to you can put the quotes in there,

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so that when you press play you out string back,

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that's even better.

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So we've learned about two methods,

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that you can implement in your classes,

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the str and the repr methods.

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The str method is called when you wanna

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turn your object into a string

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such as when printing it out

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or even when doing str of Bob

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as we have learned previously with integers.

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The repr method is used to print out

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an unambiguous representation of an abject

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so that you can use that to recreate the object for example,

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if you were a programmer looking at that output.

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Usually you'll want to implement the str method,

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but implementing the repr method can also be quite nice.

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And remember you don't have to use these two,

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they're only used for representing an object

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as a string but you don't have to do that,

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if you don't want.

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That's it for this video,

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thank you for joining me and i'll see you--