Table number iterator - twig

Question

I want to create a table in twig. The rows in the table are added dynamically, depending on what the user configures in the admin. I'm almost there, but each tr needs to be prefixed with a number.
How do I make the number (1, 2, 3) dynamic, as I don't know how many rows will be in the table beforehand? I have looked at the batch and for explanations in the twig documentation but it doesn't explain what to do when you don't know the max number.
<table class="table">
<thead>
<tr>
<th scope="col">#</th>
<th scope="col">First</th>
<th scope="col">Last</th>
<th scope="col">Handle</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">1</th>
<td>Mark</td>
<td>Otto</td>
<td>#mdo</td>
</tr>
<tr>
<th scope="row">2</th>
<td>Jacob</td>
<td>Thornton</td>
<td>#fat</td>
</tr>
<tr>
<th scope="row">3</th>
<td>Larry</td>
<td>the Bird</td>
<td>#twitter</td>
</tr>
</tbody>
</table>

Answer 1

As you didn't provide the twig code in your question I'm assuming you are building the table with a for
<table class="table">
<thead>
<tr>
<th scope="col">#</th>
<th scope="col">First</th>
<th scope="col">Last</th>
<th scope="col">Handle</th>
</tr>
</thead>
<tbody>
{% for item in items %}
<tr>
<th scope="row">{{ loop.index }}</th>
<td>{{ item.first_name }}</td>
<td>{{ item.last_name }}</td>
<td>{{ item.handle }}</td>
</tr>
{% endfor %}
</tbody>
</table>
demo