title: How do I do to concatenate 2 arrays: 1 array contains string and the other array contains int64
body: <p>I'm having a hard time trying to concatenate two arrays using numpy.
  One of the arrays have text (<code>string</code>) and the other array have numbers (<code>int64</code>).</p>
  
  <p>How do I do that?</p>
  
  <p>Using <code>np.concatenate()</code> set all the values as string and need both.</p>
  
  <p>I'm running a for loop to determinate the hyperparameters of a <code>RandomForestClassifier</code>... when the loop goes to the numbers, gives an error since is expecting the numbers and get the string <code>'1'</code> or <code>'2'</code>.</p>
  
  <p>I'm using </p>
  
  <pre><code>np.concatenate((['auto'], np.arange(20, 120, 20)), axis=0, out=None)
  </code></pre>
  
  <p>and getting</p>
  
  <pre><code>array(['auto', '20', '40', '60', '80', '100'], dtype='&lt;U11')
  </code></pre>
  
  <p>However, I need</p>
  
  <pre><code>array(['auto', 20, 40, 60, 80, 100])
  </code></pre>