title: How np.argsort works in pandas DataFrame?
body: <p>I have the following pandas DataFrame named <code>index</code>:</p>
  
  <pre><code>tz
                         521.0
  Africa/Cairo             3.0
  Africa/Casablanca        1.0   
  Africa/Ceuta             2.0
  Africa/Johannesburg      1.0
  dtype: float64 
  </code></pre>
  
  <p>when I apply <code>index.argsort()</code> I get something like this:</p>
  
  <pre><code>tz
                         2
  Africa/Cairo           4
  Africa/Casablanca      3
  Africa/Ceuta           1
  Africa/Johannesburg    0
  dtype: int64
  </code></pre>
  
  <p>Can someone explain to me where the numbers: <code>2,4,3,1,0</code> come? I know they're index range from 0 to 4 but I can't find any logic in their order.</p>