Module 11: Introduction to Turtle Graphics

First read this page and then start coding the module.
Post your Python files to Blackboard under the Module 11 assignment.

Objectives

By the end of this module, you will be able to:

Use the Turtle graphics library in Python.
Control turtle movements with basic commands.
Create simple shapes and patterns using Turtle.
Use loops to generate repeated patterns.
Customize colors and pen properties in Turtle graphics.

Getting Started with Turtle Graphics

What is Turtle?

Turtle graphics provides a visual way to see what your code does by moving a turtle (cursor) around the screen.

How to Use Turtle

Before we can use Turtle, make sure to import the library:

import turtle

This library provides all the tools to control the turtle. When you run your program, a new window will appear where the turtle will draw shapes and patterns.

Exercise 1: Open your Python editor and create a new file called turtle_intro.py. Use the following code to get started:

import turtle

# Create a turtle object
leo = turtle.Turtle()

# Set the shape of the turtle
leo.shape('turtle')

# Move the turtle forward by 100 units
leo.forward(100)

Run the program and observe the turtle moving across the screen!

Turtle Movement Commands

You can move the turtle using several commands. Below are some basic turtle movement functions:

turtle.forward(distance): Moves the turtle forward by the given distance.
turtle.backward(distance): Moves the turtle backward by the given distance.
turtle.left(angle): Turns the turtle left by the specified angle (in degrees).
turtle.right(angle): Turns the turtle right by the specified angle.

Example: Drawing a Square

Let’s use these commands to draw a square.

import turtle

leo = turtle.Turtle()
leo.shape('turtle')

# Move the turtle in a square
for i in range(4):
    leo.forward(100)
    leo.right(90)

Exercise 2: In your turtle_intro.py file, add code to draw a square, as shown above. Experiment by changing the angles and distances to create new shapes.

Customizing Your Turtle

You can customize your turtle’s appearance and how it draws on the screen.

Changing the Pen Size and Color

You can change the thickness of the lines the turtle draws and its color:

turtle.pensize(size): Changes the width of the pen.
turtle.pencolor(color): Changes the color of the turtle’s pen. You can use common color names like 'red', 'blue', or 'green'.

Example: Drawing a Colored Triangle

import turtle

leo = turtle.Turtle()
leo.shape('turtle')

# Set pen size and color
leo.pensize(5)
leo.pencolor('blue')

# Draw a triangle
for i in range(3):
    leo.forward(150)
    leo.left(120)

Exercise 3: Modify your turtle_intro.py file to draw a triangle with different pen sizes and colors. Experiment with drawing other polygons like pentagons or hexagons.

Using Loops for Repeated Patterns

We can use loops to easily create complex patterns without repeating code. For example, let’s draw a flower by repeating a simple shape.

Example: Drawing a Flower

import turtle

leo = turtle.Turtle()
leo.shape('turtle')

# Draw a flower by repeating a petal shape
for i in range(36):
    leo.forward(100)
    leo.right(60)
    leo.forward(100)
    leo.right(120)
    leo.forward(100)
    leo.right(60)
    leo.forward(100)
    leo.right(10)

Exercise 4: Create a new file called turtle_flower.py and use the code above to draw a flower pattern. Experiment by changing the angles and the number of repetitions.

Drawing Circles and Arcs

In addition to straight lines, the turtle can draw circles and arcs.

turtle.circle(radius): Draws a circle with the given radius.
turtle.circle(radius, angle): Draws an arc (a part of a circle) with the given radius and angle.

Example: Drawing a Sun

import turtle

leo = turtle.Turtle()
leo.shape('turtle')

# Draw a circle (the sun)
leo.pencolor('orange')
leo.circle(50)

# Draw sun rays
for i in range(12):
    leo.penup()      # Pick up the pen
    leo.goto(0, 50)  # Move to the center of the circle
    leo.pendown()    # Put down the pen
    leo.forward(100)
    leo.backward(100)
    leo.right(30)

Exercise 5: In a new file called turtle_sun.py, draw a sun with rays as shown above. Feel free to experiment with different colors, pen sizes, and patterns.

Changing the Turtle’s Speed

If the turtle is moving too slowly, you can change its speed using the turtle.speed() function. The speed values range from 1 (slow) to 10 (fast), or you can use 0 for the fastest speed.

Exercise 6: Add leo.speed(10) to your turtle_flower.py file and see how fast your flower is drawn! What happens when you change the speed value?

Adding Fill Colors

You can also fill shapes with colors using turtle.begin_fill() and turtle.end_fill():

turtle.begin_fill(): Starts filling the shape.
turtle.end_fill(): Stops filling the shape.

Example: Drawing a Filled Star

import turtle

leo = turtle.Turtle()
leo.shape('turtle')

# Set fill color
leo.fillcolor('yellow')

# Begin filling the star
leo.begin_fill()

# Draw a star
for i in range(5):
    leo.forward(100)
    leo.right(144)

# End filling
leo.end_fill()

Exercise 7: In a new file called turtle_star.py, create a filled star like the example above. Experiment with other shapes and colors.

Exercise 8: Using everything you’ve learned in this module, create your own unique pattern in a new file called turtle_create.py. You can use loops, colors, shapes, and other turtle features. Be creative!