Variables

Turtle Variables

A Variable

Is like a box with a label. The label tells us what’s inside the box. Coders use variables (labels) to store and remember information in a program.

t = Turtle()
u = Turtle()
r = Turtle()
t = Turtle()
l = Turtle()
e = Turtle()

By naming your turtle you can make multiple instances, giving each unique attributes. In other words, the code above makes several turtles which are the same, but each turtle has a different name (or label). You can then change each turtle using functions — making each of them different! When coming up with a name, make them short and to the point as you will be repeating these.

Using Turtle Functions

A function

A function is like a set of instructions you can use again and again in a program. Instead of writing the same steps over and over, you can put them in a function and just use that function whenever you need it! When we use t.penup(), we’re actually using a special set of instructions that someone else wrote. This set of instructions is called a function. Inside that function, there are lines of code that we can’t see directly, but they do important work.

Some Interesting Functions:

pendown() # By default the pen is down, and it will draw the line behind the turtle.
penup() # Bringing the pen up will remove this line.
width() # Width changes the thickness of the line the pen draws (in pixels).
turtlesize() # It changes the size of the turtle drawing the line.
color() # Color will change the colour of both the line and turtle.
fillcolor() #  This will change the colour inside the lines but must be used with:
    begin_fill()
    end_fill()
speed() # The speed of the turtle drawing. It ranges from 1 (slowest) up to 10 (which you can write as 0).
shape("circle"). # Changes the look of your turtle to a circle.
# You can also change it to a: square, triangle, arrow and turtle.

Examples

t.penup()
t.width(30)
r.width(10)
l.shape("circle")
e.speed(0)
u.speed(9)
u.color("green")

Note

Once your turtle has been named its name must be used to register code to that turtle. Without spaces the turtles name is followed by a fullstop and then the syntax for your required code. Instances such as the turtle and screen require capitals like pronouns in english.

Window Setup / Control

Setting up a window can help you understand parameters. For example knowing the edges of your screen means knowing how far you can draw. Screen/window set up also allows for adding background colours and clearing the canvas.

A parameter

A parameter is a special kind of variable in a function that stands for the information you give to that function. When you call the function, the values you provide are called arguments, and the parameter helps the function know what to do with those values.

But First: Let’s Assign Screen to a Variable

This will make your life easier in the long run: writing long names instead of your own label over and over can get tedious. So we can do something like this:

s = Screen()
# So instead of having to write this
Screen.bgcolor("black")
# You can do this
s.bgcolor("black")

One screen at a time

When calling the s = Screen() you create an instance. This can be the only instance active at a time.

Some useful functions:

s.setup(600, 600, 0, 0) # This dictates the screens width, height, x position and y position.
# This can also be done without setting the starting x, y positions.
s.setup(600, 600)
s.resetscreen() # Clears everything on the screen and brings the turtle back to its starting position.
s.bgcolor("")

Checklist

• I have made multiple turtles.
• I have named and changed my turtles to do different things.
• I have named and changed my screen.