python螺旋线怎么画

import turtle

n = 500

turtle.penup()

turtle.goto(-450,150)

turtle.pendown()

turtle.pencolor("blue")

for i in range(500):

    n = n - 1

    #n -= 1

    turtle.speed(100)

    turtle.fd(n)

    turtle.right(90)

turtle.pendone()