title: Numpy array, fill empty values for a single column
body: <p>I have an array in numpy, which was generated using np.array() from a python list so my entries are strings, but some of the values are blank. Here is an example array:</p>
  
  <pre><code>['1', '1', '1', '1']
  ['1', '1', '', '1']
  ['1', '1', '1', '1']
  ['1', '', '1', '1']
  </code></pre>
  
  <p>There is no 'NaN' or 'None', it is blank. I want to be able to fill all the blank cells in a particular column with the same value. </p>