title: Sierpinski triangle recursion using turtle graphics
body: <p>I am trying to write a program that draws a sierpinski tree with python using turtle. Here is my idea:</p>
  
  <pre><code>import turtle
  def draw_sierpinski(length,depth):
      window = turtle.Screen()
      t = turtle.Turtle()
      if depth==0:
          for i in range(0,3):
              t.fd(length)
              t.left(120)
      else:
          draw_sierpinski(length/2,depth-1)
          t.fd(length/2)
          draw_sierpinski(length/2,depth-1)
          t.bk(length/2)
          t.left(60)
          t.fd(length/2)
          t.right(60)
          draw_sierpinski(length/2,depth-1)
      window.exitonclick()
  
  
  draw_sierpinski(500,1)
  </code></pre>
  
  <p>The program does not reach the 2nd line after the else statement and I don't know why. Can anyone help me?</p>