python使用turtle库与random库绘制雪花

# -*- coding: utf-8 -*-
"""
Created on Fri Jan 12 14:35:14 2018

@author: Administrator
"""

from turtle import *
from random import *

def ground():
 hideturtle()
 speed(100)
 for i in range(400):
  pensize(randint(5,10))
  x=randint(-400,350)
  y=randint(-280,-1)
  r=-y/280
  g=-y/280
  b=-y/280
  pencolor(r,g,b)
  penup()
  goto(x,y)
  pendown()
  forward(randint(40,100))

def snow():
 hideturtle()
 speed(100)
 pensize(2)
 for i in range(100):
  r=random()
  g=random()
  b=random()
  pencolor(r,g,b)
  penup()
  setx(randint(-350,350))
  sety(randint(1,270))
  pendown()
  dens=randint(8,12)
  snowsize=randint(10,14)
  for j in range(dens):
   forward(snowsize)
   backward(snowsize)
   right(360/dens)

def main():
 setup(800, 600, 0, 0)
 tracer(False)
 bgcolor("black")
 snow()
 ground()
 tracer(True)
 mainloop()
main()