title: How to remove successive similar numbers in a pandas DF column
body: <p>I have a pandas DF with a column - this column can have 3 values, either 0, 1 or ' ' (see example below).
  What I want to do is remove all successive <strong>numbers</strong> that are similar. So a 0 can never be followed by a 0 and a 1 can never be followed by 1. Instead I want to replace these by a ' '.</p>
  <p><strong>Current pandas DF</strong></p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th style="text-align: left;">time</th>
  <th style="text-align: center;">value</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td style="text-align: left;">1:00</td>
  <td style="text-align: center;">0</td>
  </tr>
  <tr>
  <td style="text-align: left;">2:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">3:00</td>
  <td style="text-align: center;">0</td>
  </tr>
  <tr>
  <td style="text-align: left;">4:00</td>
  <td style="text-align: center;">1</td>
  </tr>
  <tr>
  <td style="text-align: left;">5:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">6:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">7:00</td>
  <td style="text-align: center;">1</td>
  </tr>
  <tr>
  <td style="text-align: left;">8:00</td>
  <td style="text-align: center;">1</td>
  </tr>
  <tr>
  <td style="text-align: left;">9:00</td>
  <td style="text-align: center;">0</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p><strong>What I want</strong></p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th style="text-align: left;">time</th>
  <th style="text-align: center;">value</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td style="text-align: left;">1:00</td>
  <td style="text-align: center;">0</td>
  </tr>
  <tr>
  <td style="text-align: left;">2:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">3:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">4:00</td>
  <td style="text-align: center;">1</td>
  </tr>
  <tr>
  <td style="text-align: left;">5:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">6:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">7:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">8:00</td>
  <td style="text-align: center;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">9:00</td>
  <td style="text-align: center;">0</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I tried to work with loops, but cannot find a clean way to refer to 'the next same value'.
  Any simple solution for this?</p>