Turtle is a Python library that allows us to create drawings. Imagine it like a little robot turtle on a piece of paper that has a pen and follows our instructions.
Lets start by creating a new script called Turtle.py. In order to use Turtle we need to tell our script we want to use all the functions that come with Turtle. We do this by starting our script with:
import turtle as t
This means we don't have to type turtle. in front of a function name every time we want to use one of the functions from the library - we can just use t. instead as you will see below.
Now we can start using Turtle!
The most simple way of getting the turtle to move is with the forward and backward functions. Both of these functions take one argument: the amount of pixels the turtle should move by.
t.forward(100) # Move the turtle forward 100 pixels in the direction it is facing
t.backward(50) # Move the turtle backwards 50 pixels from the direction it is facing
You may noticed with the forwards and backwards commands, the turtle only moves in the direction it is faces. However, we can change which direction it is facing! We do this with the left and right functions. Both of these functions have one argument: the angle in degrees the turtle will turn.
t.left(45) # Turn the turtle 45 degrees to the left
t.right(30) # Turn the turtle 30 degrees to the right
This functions will not move the turtle anywhere, just turn it on the spot.
💡 Exercise: Try using the
forward,backward,leftandrightfunctions to draw a square.
You might notice that the turtle window closes when the script has finished running. This doesn't give you time to admire your art work! If you would like to stop this you can add the line t.done()at the end of your script. This will tell the script that you have finished with Turtle but not close the window automatically.
Additional movement functions
While you can create all kinds of drawings with the four functions mentioned above, there are many other ways of controlling the turtle. There are some listed here or you can read about them in the Python Turtle library documentation. If you can think of way you want to move the turtle, there is probably way to do it!
Another way of controlling the turtle movement is by telling it directly what coordinate you want it to go to. It will move in a straight line from where it is to the coordinate you have told it to go to, regardless of which direction it is facing.
t.goto(100, 50) # Move turtle from where is it to the coordinate (100, 50) in a straight line
You can also move the turtle to any position without drawing anything.
t.teleport(35, 75) # Move turtle from where it is to the coordinate (35, 75) without drawing anything
If you can't get this to work you can achieve the same thing by using the penup and pendown function explained below.
The turtle's home is the coordinates (0, 0) and by calling the home function you can move it from where it is to those coordinates in a straight line.
t.home() # Move turtle from where it is to (0, 0) in a straight line
In the introduction to Turtle, we mentioned that our robot turtle was holding a little pen. We can control when that pen will draw a line when the turtle moves with the following functions.
pendown() will put the pen 'down' to the digital 'paper' so that when the turtle moves, it will draw.
t.pendown() # Continue drawing
This function doesn't do anything if the pen is already down.
penup() will take the pen off the digital 'paper' so that when the turtle moves, it will not draw.
t.penup() # Stop drawing
This function doesn't do anything if the pen is already up.
💡 Exercise: Try using the previous two functions to create a dashed line.
Sometimes we may want to delete all the drawings we have made with the turtle. We can do this with the clear() function:
t.clear() # Remove all drawings
You will have noticed that so far, our turtle has only been using a small black pen. The Turtle library has functions that allow us to control what kind of line the turtle draws with its pen. We are able to control the size, colour, speed and fill.
💡 Exercise: Try drawing a square where each side changes pen size, pen colour, fill colour and speed using these functions.
The default pen size is 1 pixel. We can change what size it is with the function pensize(), for example:
t.pensize(5) # Set the pen to be 5 pixels thick
The default pen colour is black. We can change what colour it is in a handful of different ways.
t.color("pink") # Change the pen colour to pink
t.color("#ffc0cb") # Change the pen colour to the colour with HEX value #ffc0cb
t.color(255, 192, 203) # Change the pen colour to the colour with RGB values 255, 192 and 203
You can find the name, hex value or RGB value of a colour by using a online colour picker.
Note: to use the RGB values you need to set the colour mode turtle uses by adding t.colormode(255) before you call t.color().
When drawing a closed shape (all lines join up) you can choose what colour to fill the shape in with.
First set the colour with fillcolor(). Here are three different ways of doing this.
t.fillcolor("pink") # Change the fill colour to pink
t.fillcolor("#ffc0cb") # Change the fill colour to the colour with HEX value #ffc0cb
t.fillcolor(255, 192, 203) # Change the fill colour to the colour with RGB values 255, 192 and 203
The fill colour does not have to be the same as the pen colour.
Then before you draw a closed shape call begin_fill()
t.begin_fill() # Tell Turtle to fill in the shape drawn after this
Once you have finished drawing the shape you need to call end_fill()
t.end_fill() # Tell Turtle you have finished drawing the shape you want to fill
The shape will only be filled once end_fill() has been called.
You can get the speed the turtle moves at using speed().
t.speed(5) # Sets the turtle to move at speed 5
t.speed("fastest") # Sets the turtle to move at its fastest speed
The turtle has speeds 0 to 10 so you can use any number between 0 and 10 or you can use some set speed strings:
| string | value | code |
|---|---|---|
| fastest | 0 | t.speed(“fastest”) |
| fast | 10 | t.speed(“fast”) |
| normal | 6 | t.speed(“normal”) |
| slow | 3 | t.speed(“slow”) |
| slowest | 1 | t.speed(“slowest”) |
The default screen colour is white but we can change what colour it is with bgcolor(). First you need to 'get' the screen:
screen = t.getscreen()
Then here are three different ways you can change the colour of the screen:
screen.bgcolor("pink") # Change the background to be pink
screen.bgcolor("#ffc0cb") # Change the background colour to the colour with HEX value #ffc0cb
screen.bgcolor(255, 192, 203) # Change the background colour to the colour with RGB values 255, 192 and 203
💡 Exercise: Try setting the background colour to green.
You can find out what the screen size of the Turtle window is with the screensize function.
size = t.screensize()
This will return a tuple (a way of storing multiple items in a single variable). The first item in the tuple is the screen width and you can access it with:
width = size[0]
The second item is the height:
height = size[1]
You can also use the same function to set the screen size to whatever you would like.
t.screensize(100, 200)
This will make the screen a rectangle 100 pixels wide by 200 pixels tall.
There are many other functions you can call on the screen which you can read about in the Python Turtle library documentation.
Turtle is able to take some inputs from the user which you can then use in your script.
💡 Exercise: Try drawing a squares whose sides have the length the user gives.
num = screen.numinput("Favourite number", "Please enter your favourite number") # Ask the user to enter their favourite number
name = screen.textinput("Name", "Please enter your name") # Ask the user to enter their name
Next up: Challenge