title: None type object has no attribute update
body: <p>I'm Trying to make a game. Like in any other shooting game, the enemies are supposed to disappear when shot. Apparently, you can't kill surfaces, but you can kill sprites. So I'm trying to load my images as sprites, but I'm getting a weird error. I make the class, apply a variable to it, make a variable for <code>pygame.sprite.Group</code>, and add the class variable to the group. When I try to update the group, It says <code>"'NoneType' object has no attribute 'update'"</code>. Here's the code for the class:</p>
  
  <pre><code>class Spawn(pygame.sprite.Sprite):
      def __init__(self,primaryx,primaryy):
          pygame.sprite.Sprite.__init__(self)
          global directionM
          self.directionM=directionM
          x1=random.randint(100,400)
          y1=random.randint(100,400)
          self.x1=x1
          self.y1=y1
          self.primaryx=primaryx
          self.primaryy=primaryy
      def AIPrototype(self):
          minionup=pygame.image.load("Alien.png").convert_alpha()
          miniondown=pygame.image.load("Aliendown.png").convert_alpha()
          minionleft=pygame.image.load("Alienleft.png").convert_alpha()
          minionright=pygame.image.load("Alienright.png").convert_alpha()
          global x,y,posx,posy
          seperate=random.randint(1,1000)
          screen.blit(self.directionM,(self.primaryx,self.primaryy))
          if seperate==2:
              self.primaryx=x+100
          if seperate==20:
              self.primaryx=x-100
          if seperate==150:
              self.primaryy=y+100
          if seperate==200:
              self.primaryy=y-100
          self.x1=self.primaryx
          self.y1=self.primaryy
          if self.x1&lt;x:
              xspeed1=1
              slopex1=x-self.x1
          if self.x1&gt;x:
              xspeed1=-1
              slopex1=self.x1-x
          if self.y1&lt;y:
              yspeed1=1
              slopey1=y-self.y1
          if self.y1&gt;y:
              yspeed1=-1
              slopey1=self.y1-y       
      #
          hypo1=((slopex1**2)+(slopey1**2))**0.5
          speedmark1=hypo1/1
          speedy1=slopey1/speedmark1
          speedx1=slopex1/speedmark1
          movex1=speedx1
          movey1=speedy1
          if self.x1&lt;=640 and self.x1&gt;=0:
              if self.x1&gt;x:
                  self.x1+=xspeed1*movex1
                  if self.x1&lt;x:
                      xspeed1=0
          if self.y1&lt;=480 and self.x1&gt;=0:
              if self.y1&gt;y:
                  self.y1+=yspeed1*movey1
                  if self.y1&lt;y:
                      yspeed1=0
          if self.x1&lt;=640 and self.x1&gt;=0:
              if self.x1&lt;x:
                  self.x1+=xspeed1*movex1
                  if self.x1&gt;x:
                      xspeed1=0
          if self.y1&lt;=480 and self.x1&gt;=0:
              if self.y1&lt;y:
                  self.y1+=yspeed1*movey1
                  if self.y1&gt;y:
                      yspeed1=0
      #
          if self.x1&gt;640:
              self.x1=640
          if self.x1&lt;0:
              self.x1=0
          if self.y1&gt;480:
              self.y1=480
          if self.y1&lt;0:
              self.y1=0
          if self.y1&gt;=posy-20 and self.y1&lt;=posy+20 and self.x1&gt;=x-20 and self.x1&lt;=x+20:
              Spawn.kill()
          self.primaryx=self.x1
          self.primaryy=self.y1
  </code></pre>
  
  <p>And this is the game loop:</p>
  
  <pre><code>spritegroup=pygame.sprite.Group()
  spawn=Spawn(600,200)
  spritegroup=spritegroup.add(spawn)
  clock = pygame.time.Clock() 
  keepGoing = True        
  
  try:
      while keepGoing:
          clock.tick(60) 
          screen.fill(THECOLORS['red'])
          char()#start
          x+1
          posxlist.append(x)
          posylist.append(y)
          spritegroup.update()
          pygame.display.flip()
  </code></pre>
  
  <p>I realize that my code is really messy and inefficient, and I'm really sorry about that. I'm completely new to using classes and sprites.</p>