### 地球绕着太阳转月亮绕着地球转.py

```"""地球绕着太阳转月亮绕着地球转.py"""
__author__ = "李兴球"
__date__ = "2018年5月"

import pygame
from pygame.locals import *
import math

pygame.init()
screenWidth,screenHeight=480,360
screenCenterx = screenWidth//2 -1
screenCentery = screenHeight//2 -1
screen = pygame.display.set_mode((screenWidth,screenHeight))
pygame.display.set_caption("太阳系公转,地月系_地球绕着太阳转月亮绕着地球转_作者:李兴球")

class Ball():
def __init__(self,r,color,speed):
"""球的半径,颜色和每次转的角速度"""
self.image = pygame.Surface((2*r,2*r))
pygame.draw.circle(self.image,color,(r,r),r)
self.image.set_colorkey((0,0,0))
self.rect = self.image.get_rect()
self.speed= speed
self.angle = 0
self.angle = self.angle + self.speed
def draw(self):
screen.blit(self.image,self.rect)

def main():
earth = Ball(20,(0,0,255),1)
moon = Ball(10,(255,255,200),5)
clock = pygame.time.Clock()
运行中 = True
while 运行中:
for event in pygame.event.get():
if event.type==QUIT:运行中 =False
screen.fill((0,0,0))
#画个太阳在中间
pygame.draw.circle(screen,(255,11,0),(screenCenterx,screenCentery),40)
earth.move(screenCenterx,screenCentery,150)
earth.draw()
moon.move(earth.rect.centerx,earth.rect.centery,50)
moon.draw()
pygame.display.flip()
clock.tick(60)

pygame.quit()

if __name__ == "__main__":
main()
```