python：绘制美丽星空

from turtle import *  
from random import random,randint  
screen = Screen()  
width ,height = 800,600  
screen.setup(width,height)  
screen.title("模拟3D星空")  
screen.bgcolor("black")  
screen.mode("logo")  
screen.delay(0)#这里要设为0，否则很卡  
t = Turtle(visible = False,shape='circle')  
t.pencolor("white")  
t.fillcolor("white")  
t.penup()  
t.setheading(-90)  
t.goto(width/2,randint(-height/2,height/2))  
stars = []  
for i in range(200):  
    star = t.clone()  
    s =random() /3  
    star.shapesize(s,s)  
    star.speed(int(s*10))  
    star.setx(width/2 + randint(1,width))  
    star.sety( randint(-height/2,height/2))  
    star.showturtle()  
    stars.append(star)  
while True:  
    for star in stars:  
        star.setx(star.xcor() - 3 * star.speed())  
    if star.xcor()<-width/2:  
        star.hideturtle()  
        star.setx(width/2 + randint(1,width))  
        star.sety( randint(-height/2,height/2))  
        star.showturtle()