fractals.py

import turtle, sys, math

def dragon_curve(t, n, l):
    sqrt2over2 = math.sqrt(2)/2
    i = [1 for i in range(n)]
    def r(n, l):
        if n == 0:
            t.forward(l)
        else:
            _ = 1
            if i[n-1]%2 == 0: _ = -1
            t.left(_*45)
            r(n - 1, l*sqrt2over2)
            t.right(_*90)
            r(n - 1, l*sqrt2over2)
            t.left(_*45)
            i[n-1] += 1

    r(n, l)

def koch_curve(t, n, l):
    def r(n, l):
        if n == 0:
            t.forward(l)
        else:
            r(n - 1, l/3)
            t.left(60)
            r(n - 1, l/3)
            t.right(120)
            r(n - 1, l/3)
            t.left(60)
            r(n - 1, l/3)

    r(n, l)

def sierp_tri(t, n, l):
    i = [0 if i%2 == 0 else 1 for i in range(n)]
    def r(n, l):
        if n == 0:
            t.forward(l)
        else:
            _ = 1
            if i[n-1]%2 == 0: _ = -1
            t.left(_*60)
            r(n - 1, l/2)
            t.right(_*60)
            r(n - 1, l/2)
            t.right(_*60)
            r(n - 1, l/2)
            t.left(_*60)
            i[n-1] += 1

    r(n, l)

t = turtle.Turtle()
t.speed(100000)

n = int(sys.argv[1])

#for i in range(1, int(n + 1)):
#    t.home()
#    t.color(1 - i/n, 1 - i/n, 1 - i/n)
t.penup()
t.setx(-250/2)
t.pendown()
dragon_curve(t, n, 250)

turtle.done()