python - Sierpinski triangle recursion using turtle graphics -

i trying write program draws sierpinski tree python using turtle. here idea:

import turtle def draw_sierpinski(length,depth):     window = turtle.screen()     t = turtle.turtle()     if depth==0:         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) 

the program not reach 2nd line after else statement , don't know why. can me?

i don't think should creating turtle or window object inside function. since draw_sierpinski gets called 4 times if orininally call depth 1, you'll create 4 separate windows 4 separate turtles, each 1 drawing single triangle. instead, think should have 1 window , 1 turtle.

import turtle def draw_sierpinski(length,depth):     if depth==0:         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 = turtle.screen() t = turtle.turtle() draw_sierpinski(500,1) window.exitonclick() 

result:

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these results pretty depth 1 triangle, when call draw_sierpinski(100,2)?

ooh, not good. occurs because function should draw shape, , return turtle original starting position , angle. evident depth 1 image, turtle doesn't return starting position; ends halfway left slope. need additional logic send home.

import turtle def draw_sierpinski(length,depth):     if depth==0:         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)         t.left(60)         t.bk(length/2)         t.right(60)  window = turtle.screen() t = turtle.turtle() draw_sierpinski(100,2) window.exitonclick() 

result: