The presentation of a spiral-drawing program culminates in this program.

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13``` ```from turtle import * from math import * pensize(10) pencolor("blue") penup() radius = 20 goto(radius,0) pendown() for i in range(1,300): newangle = 2*i*pi/100 goto( radius*cos(newangle), radius*sin(newangle) ) radius = radius + 1 ```

Two significant changes from the earlier circle-drawing program are seen above.
First, `radius` is redefined to be one unit larger, each time variable `i` steps through its sequence of numbers. Second, the sequence of numbers is not 1-100, but instead 1-299, even though the angle variable `newangle` calculation is in terms of 1/100th of a full sweep around the circle. In effect, the larger sequence 1-299 amounts to going about three times around the circle. Drawing three times around a circle would not be needed to draw a circle, but because the radius is increasing, the program draws a spiral.

Two interesting pointers related to this example are:

• The inventor of the Python language, Guido van Rossum, also created a small drawing language for kids, Guido van Robot.

• You can actually run turtle programs in a browser, using Skulpt, which translates Python programs into Javascript programs; since Javascript is the language for controlling web page behavior, it is possible to run the equivalent of Python programs on web pages.