title: How to compare df values with the elements of a list, and make a df with those values?
body: <p>I have a dataframe like this:</p>
  <pre><code>     Name           Object
       
       Patrick        ball
       Patrick        tshirt
       Patrick        headphones          
       Leonard        ball
       Leonard        tshirt
       Leonard        pants
       Leonard        headphones
       Larry          ball
       Larry          headphones
       Larry          tshirt
       Larry          cellphone
       Maria          book
       Maria          cellphone
       Nick           computer
       Nick           ball
  
  objects=['ball','tshirt','headphones','pants','cellphone','book','computer']
  </code></pre>
  <p>I want a dataframe with the names of the persons and the missing elements in comparison with the objects list, like this:</p>
  <pre><code>    Name            Object
      
      Patrick         pants 
      Patrick         cellphone
      Patrick         book
      Patrick         computer
      Leonard         headphones
      Leonard         cellphone
      Leonard         book 
      Leonard         computer
         .               .
         .               .
         .               .
      Nick            tshit
      Nick            headphones
      Nick            pants
      Nick            cellphone
      Nick            book
  </code></pre>