def generate(n, result='[X]'):
    for _ in range(n):
        # rule #2
        result = result.replace('F', 'FF')
        # rule #1
        result = result.replace('X', 'F-[[X]+X]+F[+FX]-X')

    return result


def draw(cmds, size=2):
    stack = []
    for cmd in cmds:
        if cmd == 'F':
            tr.forward(size)
        elif cmd == '-':
            tr.left(25)
        elif cmd == '+':
            tr.right(25)
        elif cmd == 'X':
            pass
        elif cmd == '[':
            stack.append((tr.position(), tr.heading()))
        elif cmd == ']':
            position, heading = stack.pop()
            tr.penup()
            tr.setposition(position)
            tr.setheading(heading)
            tr.pendown()
        else:
            raise ValueError('Unknown Cmd: {}'.format(ord(cmd)))
    tr.update()


def setup():
    tr.hideturtle()
    tr.tracer(30, 0)
    tr.left(90)
    tr.penup()
    tr.goto(0, -tr.window_height()/2)
    tr.pendown()


setup()
plant = generate(6)
draw(plant, 4)
tr.exitonclick()