title: Count the number of occurrences from a column
body: <p>Be a DataFrame in pandas of this format:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>time</th>
  <th>other</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>0</td>
  <td>81219</td>
  <td>blue</td>
  </tr>
  <tr>
  <td>0</td>
  <td>32323</td>
  <td>green</td>
  </tr>
  <tr>
  <td>1</td>
  <td>423</td>
  <td>red</td>
  </tr>
  <tr>
  <td>1</td>
  <td>4232</td>
  <td>blue</td>
  </tr>
  <tr>
  <td>1</td>
  <td>42424</td>
  <td>red</td>
  </tr>
  <tr>
  <td>2</td>
  <td>42422</td>
  <td>blue</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I simply want to create a DataFrame like the following by counting the number of times each row is output in the previous DataFrame.</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>number_appears</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>0</td>
  <td>2</td>
  </tr>
  <tr>
  <td>1</td>
  <td>3</td>
  </tr>
  <tr>
  <td>2</td>
  <td>1</td>
  </tr>
  </tbody>
  </table>
  </div>