title: TypeError: unsupported operand type(s) for -=: 'instance' and 'int'
body: <p>I am recieving this error multiple times within my code. I it occurring when I am using:</p>
  
  <p><code>pos -= 1</code></p>
  
  <p>The error of course is: <code>TypeError: unsupported operand type(s) for -=: 'instance' and 'int'</code></p>
  
  <p>Any help is appriciated!</p>
  
  <pre><code>def DELETE(pos, lst) :
      temp = FIRST(lst)
      # move to just before pos
      if pos == 0 :
          lst.head = temp.nxt
      elif pos == END(lst) :
          if temp.nxt == None :
              lst = MAKENULL()
          else :
              while (temp.nxt).nxt :
                  temp = temp.nxt
              temp.nxt = None
      else :
          while pos - 1 &gt; 0 :
              temp = temp.nxt
              pos -= 1
          first = temp
          second = temp.nxt
          first.nxt = second.nxt
          lst.cur = lst.head
  </code></pre>