Simple drawing with turtle¶
Introduction¶
âTurtleâ is a python feature like a drawing board, which lets you command a little character called a turtle to draw all over it!
You can use functions like turtle.forward(...) and turtle.left(...)
which can move the turtle around.
Before you can use turtle, you have to import it. We recommend playing around with it in the interactive interpreter first, as there is an extra bit of work required to make it work from files.
To start it up in Thonny type:
import turtle
You should see something like this (but if you donât see below):
For Noteable instructions click âShowâ.
To start it up in Noteable, type:
from mobilechelonian import Turtle; turtle=Turtle()
Youâll see this:
On some computers nothing appears until you get to the next step, so donât worry if you donât see a result yet!
Note
While it might be tempting to just copy and paste whatâs written on this page into your terminal, we encourage you to type out each command. Typing gets the syntax of Python âunder your fingersâ and can help avoid errors.
Now in your interpreter (at the >>> or In: [ ] prompt) try these:
turtle.forward(25)
turtle.left(45)
The turtle.forward(...) function tells the turtle to move forward
by the given distance. turtle.left(...) takes a number of degrees which you
want to rotate to the left. There is also turtle.backward(...) and
turtle.right(...), too.
The standard turtle which youâll see if youâre using Thonny is just a triangle.
Thatâs no fun! Make it a turtle instead with the turtle.shape() command:
turtle.shape("turtle")
So much cuter!
Unfortunately the Noteable turtle doesnât have this command, so it canât change shape â but at least itâs already a turtle!
Now put a few of these commands in a file, one after the other. For example:
import turtle
turtle.forward(40)
turtle.left(90)
turtle.forward(40)
(In Noteable you donât need âimport turtleâ as your turtle has already been created).
Feel free to experiment with these, for example changing the turtle shape in Thonny,
or using the turtle.right(...) and turtle.backward(...) commands as well.
Now you can run the code â in Thonny click 
, in Noteable press Shift-Enter.
In Thonny, youâll see that the turtle
window vanishes after the turtle finished moving! This is because
Python exits when the program endsâsince the turtle window
belongs to Python, it goes away as well. Computers only do exactly what theyâre told to, and we
didnât tell it to keep the window open. To prevent that, just put
turtle.exitonclick() at the bottom of your file. Now the window stays open
until you click on it
import turtle
turtle.shape("turtle")
turtle.forward(25)
turtle.exitonclick()
Note
Python is a programming language where horizontal indenting of text is important. Weâll learn all about this in the Functions chapter later on, but for now just keep in mind that stray spaces or tabs before any line of Python code can cause an unexpected error. You could even try adding one to check how python will complain!
Resetting the turtle display¶
In Thonny you can reset the display with:
turtle.reset()
In Noteable you can reset it by creating a new Turtle display:
turtle=Turtle()
Drawing a square¶
Note
Youâre not always expected to know the anwer immediately. Learn by trial and error! Experiment, see what Python does when you tell it different things, what gives beautiful (although sometimes unexpected) results and what gives errors. If you want to keep playing with something that creates interesting results, thatâs OK too. Donât hesitate to try and fail and learn from it!
Exercise¶
Draw a square as in the following picture:
For a square you will probably need a right angle, which is 90 degrees.
Solution¶
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
Note
Notice how the turtle starts and finishes in the same place and facing the same direction, before and after drawing the square. This is a useful convention to follow, it makes it easier to draw multiple shapes later on.
Bonus¶
If you want to get creative, you can modify your shape with the
turtle.pencolor(...) function.
How do you use this function? Before you can use a function you need to know
its signature (for example what to put between the parentheses and what those
things mean). To find this out, run help(turtle.pencolor).
Tip
Are you seeing an error like this:
NameError: name 'turtle' is not defined
when trying to view help? In Python you have to import names before you
can refer to them, so in a new Python interactive shell youâll need to
import turtle before help(turtle.color) will work.
Another way to find out about functions is to browse the online documentation.
Caution
If you misdrew anything, see Resetting the turtle display above.
Tip
As you might have read in the help, you can modify the color [1] with
turtle.color(colorstring). These include but are not limited to
âredâ âgreenâ and âvioletâ. Lots of other color names will work. Try some
out!
Drawing a rectangle¶
Exercise¶
Can you draw a rectangle too?
Solution¶
turtle.forward(100)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(100)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
Bonus¶
How about a triangle? In an equilateral triangle (a triangle with all sides of equal length) each corner has an angle of 60 degrees.
More squares¶
Exercise¶
Now, draw a tilted square. And another one, and another one. You can experiment with the angles between the individual squares.
The picture shows three 20 degree turns. But you could try 20, 30 and 40 degree turns, for example.
Solution¶
turtle.left(20)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.left(30)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.left(40)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
turtle.forward(50)
turtle.left(90)
And thatâs it for your first turtle program!¶
Footnotes