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Now the final challenge for today comes courtesy of a childhood toy that you

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might've already seen. So this is going to be our training bike,

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and it's going to be the last coding exercise before we tackle our final

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project. So what are we doing? We're making a spirograph.

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Do you remember those geometric gear shaped things

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which you would draw and draw and it would make these funky circular shapes?

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Well, that's what we're going to be doing, but with turtle.

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We're going to get our turtle to draw a number of circles each with a radius of

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a hundred in distance. And once it's done,

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we should end up with something that looks like this.

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So we're going to be using our random colors and we're going to be using the

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documentation.

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I want you to dig through the documentation and see if you can figure out how to

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draw a circle and to determine how large the circle should be.

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And then I want you to figure out how you can get it to repeatedly draw a circle

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and change the tilt of the circle by a little bit each time,

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so that you end up with that effect. Pause the video and give that a go now.

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Alright. Again,

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we're going to be scrolling through all of the available methods

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looking for something that might help us.

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I think it's going to be somewhere in the turtle motion's move and draw section.

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And if you look down this list,

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you can see there is a method that allows us to draw a circle with a given

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radius.

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So we can put in the radius as one of the inputs and draw our circle. Heading

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back to our code,

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I'm going to delete some of the previous parts where we've got the directions

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and also changing the pen size.

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I'm going to leave the speed as fastest because we're going to need it to go

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pretty quick to draw all of those circles.

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And I'm also going to delete the final for loop.

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Now notice how I've got this warning here telling me that it doesn't really like

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the idea of me calling a variable the same as the name of a function.

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So why don't we just call this color instead

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and then we can return that as the output and get rid of that warning.

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Now we're ready to code up our spirograph.

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So the first thing that we're going to try and do is to draw a circle.

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Now the circle requires a radius,

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so I'm going to give it a radius of a hundred. And when I hit run,

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we can see briefly that it painted a circle.

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So let's go ahead and create our screen from t.screen.

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And then we can use that screen.exitonclick method so that when we run our

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code, it doesn't actually remove the window until we click on it.

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So I can see that I've painted my first circle

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and I would like, if possible, to make my circle

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have a different color each time.

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So I'm going to change the color to use a random color that's produced by this

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function. So now every time I run my code,

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you'll see a different colored circle.

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The turtle is basically gonna draw out this path and then go back to its

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original position facing East.

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If we wanted multiple circles to overlap with each other,

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then we're going to have to change the heading or the pointing direction of our

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turtle. If we look at this section,

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the current state of our turtle,

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you can see that you can get the current position,

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the current Y coordinate and X coordinate,

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but you can also get hold of the current heading,

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so which direction it's pointing towards.

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And all we have to do is just call this heading method.

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So now if I print my tim.heading,

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then you can see that when I run my code and I take a look inside the console,

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it's pointing at 0.0.

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What if we could change the heading to make it a little bit shifted?

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Well,

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there's actually a different method for changing the heading and getting the

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heading. For example, if we want to set the heading,

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then we have to use this method and give it a number.

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So what if I get the current heading

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and then maybe I add 5 or 10 degrees to it,

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and then I change my turtle's heading using set

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heading to the current heading plus 10.

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And then we get a new circle drawn. So let's see what this looks like.

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And you can see that I've drawn one circle and then I've tilted to the left a

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little bit and then drawn a second circle. So extrapolating this,

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you can imagine that if we had a loop that kept going,

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then we could draw our final spirograph shape.

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Let's create that loop.

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So the parts that don't need to be in the loop is setting the speed.

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But the color needs to change each time,

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the circle needs to be drawn each time and the heading needs to be updated each

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time.

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Now I'm going to simplify this line of code to contract it into a single line.

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So I'm setting Tim to a new heading

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and that is from the current heading plus 10.

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So now let's create our loop and let's say

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we're going to loop a hundred times.

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Now let's run our code and see what it looks like.

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You can see it's drawing out our spirograph.

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It's not as dense as it previously was,

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but look at what it's doing.

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It's drawing the same circle on top of a previous circle,

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cause it doesn't know when to stop.

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It's stopping only once it's gone through the hundred rotations.

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So how can we figure out a way to get it to only draw as many circles as we

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need?

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Let's say that I created a new function called draw_spirograph,

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and this function accepts a single parameter,

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which is the size of the gap.

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And that is going to be the size that's going to be in between each of these

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circles that gets drawn.

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And that's of course determined by the direction heading of my arrow.

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So if I pass in this size of gap,

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I'm going to use it here to change the tilt of my circle.

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But I can also use that because it's a degree to determine how many times my

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spirograph needs to be drawn.

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So we know that there's 360 degrees in a full circle.

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And for each circle that we're drawing,

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we're basically giving it a different offset right? And

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that's our size_of_gap.

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So if we divide 360 by each offset,

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then we'll repeat our code for as many times as we need to draw all the circles

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and complete the final spirograph. Now,

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the only problem is if I call this method,

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dra, I think I meant to write draw.

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So draw spirograph and I give it a size of five.

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So a little bit smaller than last time,

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tilting a little bit less each time. You can see that if I run this code,

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we get an error.

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And the error says that the float object can't be used as an integer

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and it's telling us where we have that float object.

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So remember that this number is going to go into here

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and then 360 divided by five is actually going to give us a floating point

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number, even though it divides cleanly

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just because this is how division works in Python. Now,

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unfortunately though our range function is going to need a whole number,

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an integer.

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It can't take a floating point number because then how many times are we

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repeating it? 3.4 times? What does that even mean?

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So this input has to be a whole number.

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So let's turn it into an integer by creating an integer and then wrapping this

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calculation inside the brackets. So now when we run our code,

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you can see it paints our spirograph, shifting by five degrees each time.

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And once it's gone through all of the iterations and the spirograph is

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complete, then it actually stops.

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Did you manage to get the solution for this challenge?

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If not, be sure to review this lesson and fix your code as needed. Once you're

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happy with everything that we've explained so far,

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then it's time to head to the final challenge.

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Let's go ahead and create a million dollar painting.

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So for all of that and more, I'll see you on the next lesson.