spiral.py

import turtle
t = turtle.Pen()
t.ht()
t.speed(0)
turtle.colormode(255)

rgb = [255, 0, 0]

def progressrainbow(rgb):
    new = []
    r, g, b = rgb
    if b == 0 and r > 0:
        r -= 1
        g += 1
    elif r == 0 and g > 0:
        g -= 1
        b += 1
    elif g == 0 and b > 0:
        b -= 1
        r += 1
    return r, g, b

def spiral(angle):
    for x in range(900):
        global rgb
        rgb = progressrainbow(rgb)
        t.pencolor(rgb)
        t.fd(x)
        t.left(angle)
spiral(89)
print "done!"
turtle.getscreen().getcanvas().postscript(file="output.eps")