title: regarding avoiding using column as index by default in Pandas
body: <p>I have a dataframe, which has two columns, the following is the screenshot of printing it out directly.  However, when printing out its columns, only one column is shown. I guess the first column is used by index by default, how can I add one extra index column, and avoid using history_date column as index.</p>
  
  <p><a href="https://i.stack.imgur.com/cFT8n.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cFT8n.png" alt="enter image description here"></a></p>
  
  <p><a href="https://i.stack.imgur.com/z4CjG.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/z4CjG.png" alt="enter image description here"></a></p>