title: Appending a new row to a numpy array
body: <p>I am trying to append a new row to an existing numpy array in a loop. I have tried the methods involving append, concatenate and also vstack none of them end up giving me the result I want.</p>
  
  <p>I have tried the following:</p>
  
  <pre><code>for _ in col_change:
  if (item + 2 &lt; len(col_change)):
      arr=[col_change[item], col_change[item + 1], col_change[item + 2]]
      array=np.concatenate((array,arr),axis=0)
      item+=1
  </code></pre>
  
  <p>I have also tried it in the most basic format and it still gives me an empty array.</p>
  
  <pre><code>array=np.array([])
  newrow = [1, 2, 3]
  newrow1 = [4, 5, 6]
  np.concatenate((array,newrow), axis=0)
  np.concatenate((array,newrow1), axis=0)
  print(array)
  </code></pre>
  
  <p>I want the output to be [[1,2,3][4,5,6]...]</p>