Turtle Graphics

In this notebok, we will demonstrate the benefit of code reuse with turtle, which is a module for drawing graphics.

Start to move the turtle¶

Because Jupyter notebook does not fully support turtle (the Tkinter GUI toolkit), we will use Thonny under the Linux Desktop instead.

How to start a python script in Thonny?

• Open a Desktop from the Launcher.
• Open Thonny via Application->Development->Thonny from the menu at the top left corner.
• Create a new Python script via File->New.
• Save the file using File->Save as... to myscript.py under the Lab4 directory.

How to move the turtle?

Type the following in your python script to import a turle and instruct it to move forward 100 steps:

import turtle as t

t.forward(100)
t.exitonclick()

To get the turtle moving, press F5 or click the green play button in the toolbar:

To exit, simply click on the display window.

Draw polygons¶

How to have the turtle draw a triangle?

The following code draws a red equilateral triangle:

t.left(120) rotates the turtle to the left by 120 degrees.

How to draw a square, a regular pentagon, or even any regular polygon?

Instead of writing a new script for each polygon, we can write a function:

def polygon(n, edge, color):
    """Draw a colored polygon.

    A function using turtle to draw a polygon 
    with arbitrary color and number of edges.

    Parameters
    ----------
    n: int
        number of edges.
    edge: int
        length of each edge.
    color: string
        color of the polygon
    """
    ...

Tesselation¶

Tessellation problem

Tessellation refers to the problem of using geometric shapes to tile a flat plane. E.g., rhombitrihexagonal tiling is a beautiful tessellation often used by temples and museums. Each hexagon is surrounded by 6 triangles and 6 squares.

The following code draws:

from polygons import *

t.speed('fast')
edge = 50

t.left(180)
hexagon(edge, 'red')
t.right(180)

for _ in range(6):
    t.left(30)
    triangle(edge, 'yellow')
    t.right(90)
    square(edge, 'purple')
    t.forward(edge)
    
t.hideturtle()
t.exitonclick()