title: how to (simply) build a integer and float mixed numpy array
body: <p>I would simply like to create a numpy array of size(N,m) that has just the first column made of integer, and the rest by default float. 
  So that, if initialized to zero it should be results:</p>
  
  <pre><code>array([[ 0,  0.,  0.,  0.,  0.],
         [ 0,  0.,  0.,  0.,  0.],
         [ 0,  0.,  0.,  0.,  0.],
         [ 0,  0.,  0.,  0.,  0.],
         [ 0,  0.,  0.,  0.,  0.]])
  </code></pre>
  
  <p>All the attempts I have made return me some tuple sub-elements when trying to create such a structured array.</p>