title: Merging pandas columns (one-to-many)
body: <p>I am new to Python’s Pandas. I want to combine several Excel sheets by a common ID. Besides, there it is a one-to-many relationship.</p>
  <p>Here are the inputs:</p>
  <p><strong>df1</strong>:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>Name</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>3763058</td>
  <td>Andi</td>
  </tr>
  <tr>
  <td>3763077</td>
  <td>Mark</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p><strong>df2</strong>:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>Tag</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>3763058</td>
  <td>item1</td>
  </tr>
  <tr>
  <td>3763058</td>
  <td>item2</td>
  </tr>
  <tr>
  <td>3763058</td>
  <td>item3</td>
  </tr>
  <tr>
  <td>3763077</td>
  <td>item4</td>
  </tr>
  <tr>
  <td>3763077</td>
  <td>item5</td>
  </tr>
  <tr>
  <td>3763077</td>
  <td>item6</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I would now like to merge the two pandas data frames df1 and df2 into the following output (the column tag is merged in a single column per ID):</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>Name</th>
  <th>Tag</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>3763058</td>
  <td>Andi</td>
  <td>item1, item2, item3</td>
  </tr>
  <tr>
  <td>3763077</td>
  <td>Mark</td>
  <td>item4, item5, item6</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>Could anybody please help me with this?</p>
  <p>Cheers,
  Andi</p>