Python-Turtle绘制具有3条主干的递归树

import turtle

canvas = turtle.Screen()
pen = turtle.Turtle()

pen.penup()
pen.goto(0, -200)
pen.setheading(90)
pen.pendown()

def draw_tree(branch_length, angle):
    if branch_length < 5:
        return
    else:
        pen.forward(branch_length)
        pen.right(angle)
        draw_tree(branch_length * 0.7, angle)
        pen.left(angle * 2)
        draw_tree(branch_length * 0.7, angle)
        pen.right(angle)
        pen.backward(branch_length)

draw_tree(100, 30)

turtle.done()