Simple drawing with turtle

Introduction

Turtle is like a drawing board.

It has functions like turtle.forward(...) and turtle.left(...) which can move the turtle around.

Before you can use turtle, you have to import it:

import turtle

turtle.forward(25)

turtle.left(30)

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 are turtle.backward(...) and turtle.right(...), too.)

If you put the commands into a file, you might have recognized that the turtle window vanishes after the turtle finished its movement. To prevent that, just put turtle.exitonclick() at the bottom of your file. Now you can click on the window to close it.

import turtle

turtle.forward(25)

turtle.exitonclick()

Drawing a square

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

As per convention, we want to terminate all figures in our starting position. This will make it easier to draw multiple shapes later on.

Bonus

If you want to get creative, you can modify your shape with the turtle.width(...) and turtle.color(...) functions. If you cannot figure out the signature of a function (that is the syntax and semantics of it, say, number of parameters and their meaning) you can use help(turtle.color).

Caution

If you misdrew anything, you can tell turtle to erase its drawing board with the turtle.reset() directive.

Drawing a rect

Exercise

Can you draw a (non-square) 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? (A triangle with 120 degrees angles will have all sides equally sized.)

More squares

Exercise

Now, draw a tilted square. And another one, and another one. You can experiment with the angles between the individual squares.

Try 20, 90 and 180 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(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(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)