File:Dragon curve.png

#
# Dragon curve
#

from xturtle import *

def fold(direction):
	if direction == 0:
		p.right(90)
	else:
		p.left(90)

def next(kette):
	kette.append(1)
	laenge = len(kette)
	for i in range(0, laenge-1):
		kette.append(kette[i])
	if kette[laenge-1+laenge/2] == 0:
		kette[laenge-1+laenge/2] = 1;
	else:
		kette[laenge-1+laenge/2] = 0;
	return kette

def zeichne(kette):
	p.tracer(100)
	p.hideturtle()
	for i in kette:
		p.forward(2)
		fold(i)
	p.forward(2)
	p.update()

def find_iteration(n):
	kette = [1]
	for i in range(1, n):
		kette = next(kette)
	return kette

def set_back():
	p.penup()
	p.goto(0,0)
	p.pendown()


it = 15

p = Pen()
zeichne(find_iteration(it))
set_back()
p.color('red')
zeichne(find_iteration(it))
set_back()
p.color('blue')
zeichne(find_iteration(it))
set_back()
p.color('green')
zeichne(find_iteration(it))
raw_input()