title: Pygame: TypeError: Invalid end position argument
body: <p>While running this code: </p>
  
  <pre><code>for p in self.particles :
         pos1 = p.pos
         pos2 = p.pos[0]+2*p.vel[0], p.pos[1]+2*p.vel[1]
         pygame.draw.line(self.screen, p.color, pos1 , pos2 , 2)
  </code></pre>
  
  <p>I keep getting this error:  </p>
  
  <blockquote>
    <p>TypeError: Invalid end position argument`  </p>
  </blockquote>
  
  <p>So I use a <code>print p.pos</code> statement to see what p.pos is and it magically works!<br>
  But the only problem is that printing it out makes the game run at like 10 frames a second...<br>
  So how do I fix the error?</p>