title: convert numpy string array into int array
body: <hr>
  
  <p>I have a numpy.ndarray</p>
  
  <pre><code>a = [['-0.99' '' '0.56' ..., '0.56' '-2.02' '-0.96']]
  </code></pre>
  
  <p>how to convert it to int?</p>
  
  <p>output : </p>
  
  <pre><code>a = [[-0.99 0.0 0.56 ..., 0.56 -2.02 -0.96]]
  </code></pre>
  
  <p>I want 0.0 in place of blank ''</p>