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Instructor: All right, your head must be spinning

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because of all these looping.

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That's a really bad joke.

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But I thought it was funny because I've been recording

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for hours now and I think I'm going a little kooky.

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So this is gonna be my last video for the day,

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not for the course,

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but we're gonna do a little fun exercise.

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Now, I call all exercises fun.

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Obviously I'm biased, but this one's especially fun.

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What are we going to do?

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Well, we're going to simulate what a computer does

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when we have something like a graphical user interface.

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That is, a computer is able to display,

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let's say even an image over here, right?

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I can see the robot over here.

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I can see the mouse.

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This is a graphical user interface.

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I see pictures, I see images on my screen,

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these pixels on my screen, and I can control them.

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Well, we're gonna create a basic version of this

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to show you how a computer would work

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just from the stuff that we've learned up until now

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using loops and using conditional logic.

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So what are we going to do?

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Well, this is the exercise,

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and you can check out the ripple here

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or you can recreate this, or again, in this video,

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you should have resources attached

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that you can play with it yourself.

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And what I want you to do is I want you

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to loop through this list of lists

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and every time you encounter a zero, I want you to display

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on the screen over here an empty space

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because a zero in a computer denotes nothing, right?

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We want a blank on the screen.

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However, when I see a one, I wanna simulate a pixel, right,

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that tiny, tiny dot on our computers

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that can be full of colors.

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It could be green, it can be blue, it can be orange.

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But for our case, I want it to be a star.

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And using that,

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I want you to create a program that takes this picture

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that let's say is in our database

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or in our computer's hard drive and displays it

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on the screen using space or multiply.

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And all I want you to do is when I click run,

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I want you to display that image right here.

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All right, this is a little tough one

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and I'm kind of letting you figure out on your own.

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But trust me, you've learned all the tools necessary

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to do this.

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Pause the video, give it a go,

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otherwise, I'm gonna show you how it's done.

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So the very first thing I like to do

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is to think about what I'm about to do.

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I wanna make sure that we have a plan in mind.

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So I'm going to comment first,

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and I'm going to say,

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while we definitely wanna iterate over picture, right?

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So we're gonna do some sort of iteration here.

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So that's number one.

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And then in here, I wanna say that if it's a zero,

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then I wanna print an empty space.

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And if it's a one, I wanna print a star,

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right?

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So that's the plan.

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Okay, so this shouldn't be too hard.

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Actually, before you get started, in order for this to work,

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you need to google a special parameter

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or a special option that you can give the print function.

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And as a matter of fact,

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the print function that you need to add

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or the option that you need to add is this end option.

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And if we scroll down, it doesn't display it that well.

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But you can see here, string appended after the last value.

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So the default when we print something is a new line

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but ideally, we might not want a new line.

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So when that happens, you might have to use this end option.

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Now, I know I left it really vague.

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I want you to practice Googling this.

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And figuring out from your mistake,

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you're gonna have a bug when you create this code,

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when you try to display this information.

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But try to solve it using the tools that you have

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of problem solving.

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All right.

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Enough talk. Let's get to it.

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So the first thing I wanna do is iterate over the picture.

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I'm going to say for image in picture because,

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well, this is one picture right here.

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So this is the picture, but it's inside of a list

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because we can have multiple pictures.

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And then, I'm going to loop once again

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over this individual list.

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So once again, I need to do a for loop.

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And this time I'm going to say for pixel

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because each one of this is a pixel in the image.

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So this is a nested for loop.

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Now, I'm going to add a conditional and say,

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if pixel equals one,

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then I'm going to print a star.

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Otherwise, I'm going to print an empty string.

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Well, maybe not empty, right?

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Because we do want a space, a blank space in the image.

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All right, so let's see if this works.

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If I click run, hmm, that's not really what I wanted.

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I want a clear image here,

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but I'm just getting things one in line.

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And remember, this was the little trick

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where every time it prints, it creates a new line.

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The default, again, if we close this, you'll see,

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is that end equals to this escape sequence of new line.

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So we can change that by simply saying, star, comma, end.

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And then I'm going to say for the end,

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I don't want a new line.

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I just want, well, a string, but an empty string.

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And same over here.

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If I do comma,

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end, and if I click run.

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All right, it's getting a little bit better

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but now I have an issue where we don't have any new lines.

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Everything is on one line.

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Hmm, that's not good.

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How can we solve this?

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Well, ideally, at the end of this first loop

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where we're just going the image or the line in the image,

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at the end of this, we create a new line right here, right?

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So again, looking at the indentation,

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I don't want a new line on every pixel

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which we had the first time.

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But I also wanna add a line between the lists of rows.

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So maybe a better name for this will be a row in picture.

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And in here, I'm going to add at the end of this for loop,

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so after we're done looping through the entire row,

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the bottom here, I'm going to print an empty line.

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But remember, the default is gonna be a new line.

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So again, an empty string,

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it's going to default to a new line.

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And we're still gonna have this code.

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If I run this, I get an error because image is not defined

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because I've just changed this to a row.

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So let's do row here.

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Click run,

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and look at that.

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We have our beautiful Christmas tree.

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If you don't think this is beautiful,

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this is the best I could.

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But this is a Christmas tree.

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And we finally have it displaying.

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We've used loops, we've used conditional logic,

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and we used a little Googling to figure out,

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hey, we need this option.

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Now our code works, but I wanna do something better here.

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And in the next video, I wanna clean up this code

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a little bit and cover a very important topic when it comes

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to programming.

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I'll see you in that one.

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Bye bye.