title: How to "append" to personalised ROS array message in python
body: <p>I defined the two following message structures for a ROS package:</p>
  
  <p>point.msg</p>
  
  <pre><code>float64 x
  float64 y
  </code></pre>
  
  <p>points.msg</p>
  
  <pre><code>point[] points
  </code></pre>
  
  <p>I am instantiating and filling a points array in Python as follows:</p>
  
  <pre><code>point_list = points()
  pt = point()
  for element in self.points:
       pt.x = element[0,0]
       pt.y = element[1,0]
       point_list += (pt,)
  </code></pre>
  
  <p>And this is the error I am getting:</p>
  
  <pre class="lang-none prettyprint-override"><code>unsupported operand type(s) for +=: 'points' and 'tuple'
  </code></pre>
  
  <p>PS : tried <code>.append</code> and it is still not working</p>