title: How can I enumerate a sublevel in a multiindex in pandas simply?
body: <p>I would like to create a new column with the enumeration of Objects column based on membership in Name</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Name</th>
  <th>Objects</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>A</td>
  <td>phone</td>
  </tr>
  <tr>
  <td>B</td>
  <td>phone</td>
  </tr>
  <tr>
  <td>B</td>
  <td>keys</td>
  </tr>
  <tr>
  <td>B</td>
  <td>chewing gum</td>
  </tr>
  <tr>
  <td>C</td>
  <td>radio</td>
  </tr>
  <tr>
  <td>C</td>
  <td>chewing gum</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>into</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Name</th>
  <th>Object no.</th>
  <th>Objects</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>A</td>
  <td>1</td>
  <td>phone</td>
  </tr>
  <tr>
  <td>B</td>
  <td>1</td>
  <td>phone</td>
  </tr>
  <tr>
  <td>B</td>
  <td>2</td>
  <td>keys</td>
  </tr>
  <tr>
  <td>B</td>
  <td>3</td>
  <td>chewing gum</td>
  </tr>
  <tr>
  <td>C</td>
  <td>1</td>
  <td>radio</td>
  </tr>
  <tr>
  <td>C</td>
  <td>2</td>
  <td>chewing gum</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I suppose that there should be a really easy way to do it</p>