Triangulo de Sierpinski a la Logo

import turtle
import math
import sys

COMPLEMENT=120
FACTOR = math.sqrt(3)/2

class Carpet:
  def __init__(self, x, y, side):
    self.x = x
    self.y = y
    self.side = side
    self.height = FACTOR*side

  def _children(self, x, y, side, height, step=0):
    if step==0:
      yield (x, y)

    else:
      newSide = side/2
      newHeight = height/2

      for f in self._children(x, y, newSide, newHeight, step - 1):
        yield f
      for f in self._children(x + newSide, y, newSide, newHeight, step - 1):
        yield f
      for f in self._children(x + newSide/2, y + newHeight, newSide, newHeight, step - 1):
        yield f

  def children(self, step=0):
    return self._children(self.x, self.y, self.side, self.height, step)


def paintTriangle(t, x, y, size):
    t.penup()
    t.goto(x, y)
    t.pendown()
    t.fillcolor(0, 0, 0)
    t.begin_fill()
    t.forward(size)
    t.left(COMPLEMENT)
    t.forward(size)
    t.left(COMPLEMENT)
    t.forward(size)
    t.end_fill()
    t.left(COMPLEMENT)

if __name__ == '__main__':
  try:
    steps = int(sys.argv[1])
  except IndexError:
    steps = 3

  sw, sh = turtle.screensize()
  size = 2*sh
  tx = -sh
  ty = -math.sqrt(3)/4*size

  t = turtle.Pen()
  t.hideturtle()
  t.speed('fastest')
  carpet = Carpet(tx, ty, size)

  turtle.tracer(False)
  triangles = 0
  for x, y in carpet.children(steps):
    paintTriangle(t, x, y, size/2**steps)
    triangles += 1
    turtle.title('Number of triangles: ' + str(triangles))
    turtle.update()

  turtle.title("Sierpinski's triangle <" + str(triangles) + " triangles>")
  turtle.exitonclick()