问如何在python中找到顶点(海龟图形)？

EN

#! /usr/bin/python3

from turtle import Turtle, Screen
turtle, screen  = Turtle(), Screen()

##~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

screen.setup( width = 600, height = 600 )
screen.title('Maximum Recursion')
turtle.speed( 0 )

maxY = 0  ##  empty forward-declaration

def recursive_draw( step, length ):
    global maxY

    turtle.forward( length )
    turtle.right( 7 )

    if turtle.ycor() > maxY:  maxY = turtle.ycor()  ##  update when needed

    if step > 0:  recursive_draw( step -1, length *0.8 )

for i in range( 50, 130 ):
    turtle.penup()
    turtle.setheading( i )
    turtle.setpos( 0, -300 )
    turtle.pendown()
    recursive_draw( 20, i )

turtle.hideturtle()
print( maxY )

screen.exitonclick()

##  eof  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~