Lesson 6 Turtle Graphics

Try the following commands in Python:

import turtle

Try making the window size a little smaller so that it’s easier to work with.

Try changing the background color of the screen to blue:

The bgcolor() function is a prewritten block of code that changes the background color of the turtle’s screen to one you decide.

Here is what is happening:

1. We tell the computer which object we want to interact with. In this case, it’s the Screen. Because the Screen object belongs to the turtle module, we make this connection known using the dot notation. So, we are telling the computer that we want to specifically use the Screen object that belongs to the turtle module, we use a dot (.) in between them. That’s how we get the first part: 

2. But we are not finished yet! We still have to tell the computer to use a specific function that belongs to the Screen object to change the color. In our case, it’s the bgcolor() function. Just as before, we put a dot in between the Screen object and the name of the function we want to use:

Finally, we give the bgcolor() function a color:

3. So altogether, the computer understands our code to mean:

• Please find the turtle module’s Screen object.
• When you do, find the bgcolor() function that belongs to it.
• Finally, do what the bgcolor() function says to do with the color we’ve given it. In this case, it is blue.

Remember, we didn’t write the code for this; it’s already written for us in the turtle module. That’s why we needed to import the turtle module first before using it. Now, the computer can go through the turtle module’s code, find the objects and functions we are asking it to use, and run the code that is already written for us.

Colors and Size

You can change the color of the turtle by specifying the name of the color or the color code. Here are the color codes for the common colors used:

blue, green, red, yellow, orange, white, black, brown, gray, pink, purple, aqua, maroon, crimson, violet, magenta.

Try the following commands:

Try changing the color of the turtle to different colors.

The turtlesize() function uses three numbers as its input: The first and second numbers are used to stretch the turtle lengthwise (up and down) and widthwise (left and right) a certain amount. The third number sets the size of the turtle’s outline (to make the line thinner or thicker).

Moving the Turtle

Try the following commands:

Creating a Pen

Drawing a Square

Filling Shapes With Color

Drawing a Star

Stamp Function

The stamp() function “stamps” a copy of the shape you select each time you use it. Let’s try the stamp() function using a turtle shape.

Let’s try the stamp() function again, but this time using a loop.

import turtle
import random
#creates a stamp
stamp=turtle.Turtle()
#make it a turtle shape
stamp.shape('turtle')
#lift the color of the stamp so we don't draw a continuous line
stamp.penup
#set RGB color mode to allow random colors in RGB
turtle.colormode(255)
#set some variables
#one for the initial distance to move (paces)
# and three more to hold the starting color values
paces = 20
random_red=50
random_green=50
random_blue = 50
#start a for loop to repeat the stamping code
#repeat for 50 times
for i in range(50):
    #use the random function to pick a random number for the red value
    random_red=random.randint(0,255)
    #repeat random function for green
    random_green=random.randint(0,255)
    #repeat random function for blue
    random_blue = random.randint(0,255)
    #set the stamp color with the randomly chosen RGB values
    stamp.color(random_red, random_green, random_blue)
    #stamp a turtle with the colors from the last step
    stamp.stamp()
    #add more paces
    paces += 3
    #move forward by the new number of paces
    stamp.forward(paces)
    #slightly turn direction as we move to start spiraling
    stamp.right(25)

Write() Function

The write() function enables you to write on the screen.

pen = turtle.Turtle()
pen.write(“Turtles rock!”)

If you wish to change the font (typestyle) and size of the text, we can give the write() function a second parameter. Here, we are using an “Open Sans” font with size 60 and a normal type (as opposed to bold).

pen.write(“Turtles rock”, font=(“Open Sans”, 60, “normal”))

Practice Questions

1. Write a program to create a red color-filled rectangle of size 400.
2. Write a program to create a yellow color-filled triangle of size 300 with orange lines
3. Write a program to create an aqua color-filled hexagon (a six-sided shape with equal sides).
4. Write a program to write your name on the screen in green letters of size 50.

Python Games

These are some games created using the help of loops. The files are provided in text format. You will need to copy the code in the file into the Thonny editor in order to run the program.