title: Change dtype of recarray column for object type
body: <p>I have a csv file where two columns (v3 and v7) are blank for all observations:</p>
  
  <pre><code>v1,v2,v3,v4,v5,v6,v7
  GNB,1980,,20,-1.168689,0.4619077,
  GNB,1981,20,-1.185176,0.4619077,
  </code></pre>
  
  <p>I am reading this into python (epd-7.0-2) using the csv2rec function:</p>
  
  <pre><code>from pylab import rec2csv, csv2rec
  all_data = csv2rec(infile)
  </code></pre>
  
  <p>When I try to augment values in the third or 7th row, I receive an error (doesn't happen for other columns):</p>
  
  <pre><code>all_data = csv2rec(infile)
  all_data.v3 = 'test'
  </code></pre>
  
  <p>RuntimeError: cannot call setfield on an object array</p>
  
  <p>So I tried changing the type, only to run into other errors:</p>
  
  <pre><code>all_data.v3.dtype = '|S30'
  TypeError: Cannot change data-type for object array.
  </code></pre>
  
  <p>An additional problem is that I am unable to change other columns in the array as well:</p>
  
  <pre><code>all_data.v1 = 'test'
  RuntimeError: cannot call setfield on an object array
  </code></pre>
  
  <p>Thoughts?  Thanks, </p>