title: Pygame's arc to be used as a sprite
body: <p>I am trying to use the pygame.draw.arc() as a sprite, but its not displaying on the screen. 
  I can achieve the same effect by writing same code in the main loop, but once I try to create a sprite, the effect is not being displayed.</p>
  
  <p>(One part in the main-loop can be un-commented to see the desired effect as well.)</p>
  
  <p>Any pointers could be of great help.</p>
  
  <pre><code>import pygame
  import random
  import math
  
  
  BLACK    = (   0,   0,   0)
  WHITE    = ( 255, 255, 255)
  RED      = ( 255,   0,   0)
  
  SCREEN_WIDTH = 513
  SCREEN_HEIGHT = 513
  class Block(pygame.sprite.Sprite):
      def __init__(self, color, width, height):
          pygame.sprite.Sprite.__init__(self)
  
          self.color = color
          self.image = pygame.Surface([width, height])
  
          self.image.fill(WHITE)
          self.image.set_colorkey(WHITE)
  
          self.center_x = SCREEN_WIDTH/2-15
          self.center_y = SCREEN_HEIGHT/2-15
          # Draw the ellipse, THIS WORKS PERFECTLY
          #pygame.draw.ellipse(self.image, color, [0, 0, width, height])
  
          self.i=0
          #THIS DOESN'T WORK FOR SOME REASON
          pygame.draw.arc(self.image, (0,255,255),(25,25,450,450),0+(self.i*math.pi)/180,math.pi/6 +(self.i*math.pi)/180,10)
          self.rect = self.image.get_rect()
          self.angle = 0
          self.radius = 210
          self.speed = 0.05
  
      def update(self):
          self.i += self.speed
  
  
  pygame.init() 
  screen = pygame.display.set_mode([SCREEN_WIDTH, SCREEN_HEIGHT])
  
  all_sprites_list = pygame.sprite.Group()
  
  block = Block(BLACK, 20, 15) 
  all_sprites_list.add(block) 
  
  done = False
  
  clock = pygame.time.Clock()
  i=0
  while not done:
      for event in pygame.event.get():  
          if event.type == pygame.QUIT: # 
              done = True  
      screen.fill(WHITE)
      all_sprites_list.update()
  
      all_sprites_list.draw(screen)
  
      #UNCOMMENT TO SEE THE DESIRED EFFECT
      #i= i+1
      #pygame.draw.arc(screen, (0,255,255),(25,25,450,450),0+(i*math.pi)/180,math.pi/6 +(i*math.pi)/180,10)
      pygame.display.flip() 
      clock.tick(60)
  
  pygame.quit()
  </code></pre>