Koch fractal with iteration

[drimades]

I tried this code for generating Koch's curve:

from turtle import *

def koch(length, depth):
   if depth == 0:
     forward(length)
   else:
     koch(length/3, depth-1)
     right(60)
     koch(length/3, depth-1)
     left(120)
     koch(length/3, depth-1)
     right(60)
     koch(length/3, depth-1)

koch(300, 2)

I'm having hard time to write an iterative version of it. Any hints/helps?