python 使用turtule绘制递归图形（螺旋、二叉树、谢尔宾斯基三角形）

import turtle
my_turtle = turtle.Turtle()
my_win = turtle.Screen()
def draw_spiral(tur, line_len):
  if line_len > 0:
    my_turtle.forward(line_len)
    my_turtle.right(90)
    draw_spiral(tur, line_len - 1)
draw_spiral(my_turtle, 100)
my_win.exitonclick()

import turtle
my_tree = turtle.Turtle()
my_win = turtle.Screen()
def draw_tree(branch_length, t):
  if branch_length > 5:
    t.forward(branch_length)
    t.right(20)
    draw_tree(branch_length-20, t)
    t.left(40)
    draw_tree(branch_length-20, t)
    t.right(20)
    t.backward(branch_length)
my_tree.left(90)
my_tree.up() # 抬起尾巴
my_tree.backward(200)
my_tree.down() # 放下尾巴
my_tree.color('green')
draw_tree(100, my_tree)
my_win.exitonclick()

import turtle
def draw_triangle(points, color, my_angle):
  my_angle.fillcolor(color)
  my_angle.up()
  my_angle.goto(points[0][0], points[0][1])
  my_angle.down()
  my_angle.begin_fill()
  my_angle.goto(points[1][0], points[1][1])
  my_angle.goto(points[2][0], points[2][1])
  my_angle.goto(points[0][0], points[0][1])
  my_angle.end_fill()
def get_mid(p1, p2):
  return ((p1[0]+p2[0])/2, (p1[1]+p2[1])/2)
def sierpinski(points, degree, my_angle):
  colormap = ['blue', 'red', 'green', 'yellow',
        'violet', 'orange', 'white']
  draw_triangle(points, colormap[degree], my_angle)
  if degree > 0:
    sierpinski([points[0],
          get_mid(points[0], points[1]),
          get_mid(points[0], points[2])],
          degree - 1, my_angle)
    sierpinski([points[1],
          get_mid(points[0], points[1]),
          get_mid(points[1], points[2])],
          degree - 1, my_angle)
    sierpinski([points[2],
          get_mid(points[2], points[1]),
          get_mid(points[0], points[2])],
          degree - 1, my_angle)
my_turtle = turtle.Turtle()
my_win = turtle.Screen()
my_points = [[-100, -50], [0, 100], [100, -50]]
sierpinski(my_points, 3, my_turtle)
my_win.exitonclick()