title: Pandas (python) Extract sum of values in different rows using one column as filter
body: <p>.Im learning data analysis and i would like to do the following. Im using pandas with google collaboratory:</p>
  <p>I have next table:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>name</th>
  <th>A1</th>
  <th>A2</th>
  <th>A3</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>First</td>
  <td>a</td>
  <td>c</td>
  <td>d</td>
  </tr>
  <tr>
  <td>Second</td>
  <td>b</td>
  <td>a</td>
  <td>a</td>
  </tr>
  <tr>
  <td>First</td>
  <td>a</td>
  <td>c</td>
  <td>d</td>
  </tr>
  <tr>
  <td>First</td>
  <td>a</td>
  <td>c</td>
  <td>d</td>
  </tr>
  <tr>
  <td>First</td>
  <td>a</td>
  <td>c</td>
  <td>d</td>
  </tr>
  <tr>
  <td>Second</td>
  <td>b</td>
  <td>a</td>
  <td>a</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I wish to sum every repeated value in columns &quot;A1&quot; to &quot;A3&quot; using the &quot;name&quot; (index) column as a filter. So the result i want is something like:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>name</th>
  <th>a</th>
  <th>b</th>
  <th>c</th>
  <th>d</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>First</td>
  <td>4</td>
  <td>0</td>
  <td>4</td>
  <td>4</td>
  </tr>
  <tr>
  <td>Second</td>
  <td>4</td>
  <td>2</td>
  <td>0</td>
  <td>0</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I have tried: data.groupby('A1').size() but first i dont know how to tell pandas to show me those result divides by group of the names in column 2</p>