tkinter 制作屏保

import random
import tkinter

class RandomBall():
    '''
    定义球的类
    '''

    def __init__(self, canvas, scrnwidth, scrnheight):
        #canvas：画布
        self.canvas = canvas
        #圆心坐标
        self.xpos = random.randint(10, int(scrnwidth)-20)
        self.ypos = random.randint(10, int(scrnheight)-20)
        #球的速度，分速度为2个轴
        self.xvelocity = random.randint(2, 5)
        self.yvelocity = random.randint(2, 5)
        #半径
        self.radius = random.randint(20, 120)
        #颜色RGB
        c = lambda: random.randint(0, 255)
        self.color = '#%02x%02x%02x'%(c(), c(), c())
        #屏幕长宽
        self.scrnwidth = scrnheight
        self.scrnheight = scrnheight

        #在画布上画球
    def create_ball(self):
        x1 = self.xpos - self.radius
        y1 = self.ypos + self.radius
        x2 = self.xpos + self.radius
        y2 = self.ypos - self.radius
        self.item = self.canvas.create_oval(x1, y1, x2, y2, fill=self.color, outline=self.color)

    #球的移动
    def move_ball(self):
        self.xpos += self.xvelocity
        self.ypos += self.yvelocity
        #球碰到屏幕边缘弹回
        if self.xpos + self.radius >= self.scrnwidth\
                or self.xpos + self.radius <= 20:
            self.xvelocity = -self.xvelocity
        if self.ypos + self.radius >= self.scrnheight\
                or self.ypos + self.radius <= 20:
            self.yvelocity = -self.yvelocity
        #球的移动函数，就是移动复制
        self.canvas.move(self.item, self.xvelocity, self.yvelocity)

class ScreenSanver():
    '''
    定义屏保
    '''
    def __init__(self):
        #把N个球放在队列中
        self.balls = []
        #球的数量
        self.num_balls = random.randint(6, 20)
        #生成框架
        self.root = tkinter.Tk()
        #取消边框
        self.root.overrideredirect(1)
        #制作透明窗口
        self.root.attributes('-alpha', 0.3)
        #任何鼠标移动都退出屏保
        self.root.bind('<Motion>', self.myquit)
        #任何键盘动作都可以退出屏保
        self.root.bind('<Key>', self.myquit)
        #得到屏幕大小规格
        w, h = self.root.winfo_screenwidth(), self.root.winfo_screenheight()
        #创建画布
        self.canvas = tkinter.Canvas(self.root, width=w, height=h)
        self.canvas.pack()

        #画布上画球
        for i in range(self.num_balls):
            ball = RandomBall(self.canvas, scrnwidth=w, scrnheight=h)
            ball.create_ball()
            self.balls.append(ball)

        self.run_screen_saver()
        self.root.mainloop()

    #球的运动函数
    def run_screen_saver(self):
        for ball in self.balls:
             ball.move_ball()
        self.canvas.after(20, self.run_screen_saver)

    #析构函数
    def myquit(self, e):
        self.root.destroy()

if __name__ == "__main__":
    ScreenSanver()