title: Why df[[2,3,4]][2:4] works and df[[2:4]][2:4] does not in Python
body: <p>suppose we have a datarame</p>
  
  <pre><code>import pandas as pd
  df = pd.read_csv('...')
  df
    0 1 2 3 4
  0 1 2 3 4 5
  1 1 2 3 4 5
  2 1 2 3 4 5
  3 1 2 3 4 5
  4 1 2 3 4 5
  </code></pre>
  
  <p>Why one approach is working and other returns syntax error?</p>