title: how to merge two dataframe's one having empty data
body: <p>have two df's </p>
  
  <p>df1 and df2</p>
  
  <p>df1 : </p>
  
  <pre><code>   21   |   20   |   1   |  2   | 3  | 4 | 5  | 8 | 9 | 10
  </code></pre>
  
  <p>df2 :</p>
  
  <pre><code>1   |   2    |   3    |  4   | 5  
  abc     asdf    df       132   248
  ban     cat     ball     bcd   aisc
  </code></pre>
  
  <p>how to merge two df so that i can get the desired output</p>
  
  <p>output needed :</p>
  
  <pre><code>  21   |   20   |   1   |  2   | 3  | 4   |   5  | 8  | 9   | 10
    nan      nan     abc     asdf  df   132     248  nan  nan   nan
    nan      nan     ban     cat   ball bcd     aisc nan  nan   nan
  </code></pre>