Posted onMay 28, 2021 • Edited onJun 4, 2021

Rainbow and Clouds with Python Turtle

#python #turtle #graphics #tutorial

In the previous posts we did

We will draw a rainbow with some clouds today. This one should be especially fun for kids because of the brights colors and the joyful objects that we will be drawing

Setting up the screen

To set up the stage let's first configure the height and the width of the canvas. We need thescreensize command to set the size of the window, and thesetworldcoordinates command to subdivide the window into the desired number of pixels.setworldcoordinates also sets up the coordinate axes for us

importturtleastt.Screen().screensize(500,500)t.Screen().setworldcoordinates(-300,300,300,900)t.Screen().bgcolor("lightblue")

We will be using a square grid. We have also set the color tolightblue usingbgcolor

In the code above we have set the coordinate y-axis range to be within 300 and 900. This will make sense in the upcoming sections

We now have a blue sky

Draw a cloud

We will be using circles to draw a cloud but there could be multiple other ways to draw a cloud.

First start with a filled circle

importturtleastt.Screen().bgcolor("lightblue")t.color("white","white")t.begin_fill()t.circle(50)t.end_fill()

Now, lets put that code into a function

importturtleastt.Screen().bgcolor("lightblue")deffilled_circle(radius,color):t.color(color,color)t.begin_fill()t.circle(radius)t.end_fill()filled_circle(50,"white")

Filled circle function. Code does the same thing as before

Next we will draw multiple circles using the function above

importturtleastt.Screen().bgcolor("lightblue")deffilled_circle(radius,color):t.color(color,color)t.begin_fill()t.circle(radius)t.end_fill()radius=50cloud_color="white"filled_circle(radius,cloud_color)t.forward(radius)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)

Multiple calls to filled_circle at different positions

We have a cloud now! ( Hope you think so too :) )

importturtleastt.Screen().bgcolor("lightblue")deffilled_circle(radius,color):t.color(color,color)t.begin_fill()t.circle(radius)t.end_fill()defcloud(radius,cloud_color="white"):filled_circle(radius,cloud_color)t.forward(radius)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)radius=50cloud(radius)

cloud function for use later

Concentric circles

Let's work on the rainbow now. Our approach will be to use concentric filled circles to draw the rainbow. Let's see if we can get what we want by progressively reducing the radius of thefilled_circle function.

importturtleastt.Screen().bgcolor("lightblue")deffilled_circle(radius,color):t.color(color,color)t.begin_fill()t.circle(radius)t.end_fill()filled_circle(100,'red')filled_circle(95,'orange')filled_circle(90,'yellow')filled_circle(85,'green')filled_circle(80,'blue')filled_circle(75,'indigo')filled_circle(70,'violet')

Reducing radius progressively and changing the color

We have aroygbiv but the circles are not concentric

Let's see how to make the circles above concentric. Let's also use a loop

importturtleastt.Screen().bgcolor("lightblue")deffilled_circle(radius,color):t.color(color,color)t.begin_fill()t.circle(radius)t.end_fill()roygbiv=['red','orange','yellow','green','blue','indigo','violet']radius=200interval=10forr_colorinroygbiv:filled_circle(radius,r_color)radius-=interval# Move turtle a up by a littlet.left(90)t.forward(interval)t.right(90)

In the code above we move the turtle up a little every time it completes a circle. We have also stored the colors of the rainbow in a list.

There are two additional things we should do. First, a rainbow could be circular but generally we see just a portion of the rainbow. To get that effect, we can move half the rainbow off the screen. Second, the center of the rainbow should be the sky. So let's make those adjustments

importturtleastt.Screen().bgcolor("lightblue")t.Screen().screensize(500,500)t.Screen().setworldcoordinates(-300,300,300,900)deffilled_circle(radius,color):t.color(color,color)t.begin_fill()t.circle(radius)t.end_fill()defrainbow(radius=200,interval=10):roygbiv=['red','orange','yellow','green','blue','indigo','violet','lightblue']forr_colorinroygbiv:filled_circle(radius,r_color)radius-=interval# Move turtle a up by a littlet.left(90)t.forward(interval)t.right(90)rainbow(300,10)

In the code above, we have changed the screen size and set up the coordinates such that only half the rainbow shows. Also, the rainbow code is now in a function. Lastly to show the center of the rainbow as the sky,lightblue has been added to theroygbiv variable

Putting it all together

We can now use the functions that we created to draw a rainbow amongst the clouds

importturtleastt.Screen().bgcolor("lightblue")t.Screen().screensize(500,500)t.Screen().setworldcoordinates(-300,300,300,900)t.Screen().tracer(0,0)deffilled_circle(radius,color):t.color(color,color)t.begin_fill()t.circle(radius)t.end_fill()defcloud(radius,cloud_color="white"):filled_circle(radius,cloud_color)t.forward(radius)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)filled_circle(radius,cloud_color)t.right(90)defrainbow(radius=200,interval=10):roygbiv=['red','orange','yellow','green','blue','indigo','violet','lightblue']forr_colorinroygbiv:filled_circle(radius,r_color)radius-=interval# Move turtle a up by a littlet.left(90)t.forward(interval)t.right(90)t.penup()t.goto(100,900)cloud(20)t.goto(-50,850)cloud(30)t.goto(50,600)cloud(50)t.goto(200,500)cloud(5)t.goto(0,0)rainbow(300,10)t.goto(-200,500)cloud(15)t.goto(50,400)cloud(10)t.goto(50,300)cloud(10)t.Screen().update()