title: how to create a new empty array column in dataframe
body: <p>I want to create a new column with each item as an empty array in dataframe,
  for example, the dataframe is like:</p>
  
  <p><code>-</code>Index  Name<br>
   <code>-</code>0       Mike<br>
   <code>-</code>1        Tom<br>
   <code>-</code>2       Lucy </p>
  
  <p>I want to create a new column, make it like:</p>
  
  <p><code>-</code>Index Name1 Scores<br>
   <code>-</code>0     Mike  []<br>
   <code>-</code>1     Tom   []<br>
   <code>-</code>2     Lucy  []</p>
  
  <p>Because I need to append values in the arrays in the new column. How should I code?</p>