How to Output Loop. Counter in Python Jinja Template?

Question

I want to be able to output the current loop iteration to my template.

According to the docs, there is a loop.counter variable that I am trying to use:

<ul>
{% for user in userlist %}
  <li>
      {{ user }} {{loop.counter}}
  </li>
      {% if loop.counter == 1 %}
          This is the First user
      {% endif %}
{% endfor %}
</ul>

But is being outputed to my template. What is the correct syntax?

Accepted Answer

The counter variable inside the loop is called loop.index in Jinja2.

>>> from jinja2 import Template

>>> s = "{% for element in elements %}{{loop.index}} {% endfor %}"
>>> Template(s).render(elements=["a", "b", "c", "d"])
1 2 3 4

In addition to loop.index, there is also

loop.index0 (index starting at 0)
loop.revindex (reverse index; ending at 1)
loop.revindex0 (reverse index; ending at 0)
Even more at .

Answer 2

Inside of a for-loop block, you can access some special variables, such as loop.index (but not loop.counter). From the official docs:

Variable	Description
`loop.index`	The current iteration of the loop. (1 indexed)
`loop.index0`	The current iteration of the loop. (0 indexed)
`loop.revindex`	The number of iterations from the end of the loop (1 indexed)
`loop.revindex0`	The number of iterations from the end of the loop (0 indexed)
`loop.first`	True if first iteration.
`loop.last`	True if last iteration.
`loop.length`	The number of items in the sequence.
`loop.cycle`	A helper function to cycle between a list of sequences.
`loop.depth`	Indicates how deep in a recursive loop the rendering currently is. Starts at level 1
`loop.depth0`	Indicates how deep in a recursive loop the rendering currently is. Starts at level 0
`loop.previtem`	The item from the previous iteration of the loop. Undefined during the first iteration.
`loop.nextitem`	The item from the following iteration of the loop. Undefined during the last iteration.
`loop.changed(*val)`	True if previously called with a different value (or not called at all).

Answer 3

If you are using Django, use forloop.counter instead of loop.counter:

<ul>
{% for user in userlist %}
  <li>
      {{ user }} {{forloop.counter}}
  </li>
      {% if forloop.counter == 1 %}
          This is the First user
      {% endif %}
{% endfor %}
</ul>

Answer 4

Real-life example:

{% for image in item['images'] %}
    {% set image_id = item_id ~ '-preview-' ~ loop.index0 %}
    <div id="{{ image_id }}" class="overlay">
        <a class="cancel" href="#{{ item_id }}"></a>
        <div class="popup">
            {% set src = image if image.startswith('http') else '/static/images/store/' ~ item_id ~ '/' ~ image %}
            <a href="{{ src }}"><img class="modal-img" src="{{ src }}"/></a>
        </div>
    </div>
{% endfor %}

Answer 5

In your Python code:

env = Environment(loader=FileSystemLoader("templates"))
env.globals["enumerate"] = enumerate

In your template:

{% for idx, val in enumerate(list) %}
    {{ idx }}. {{val}}
{% endfor %}

How to Output Loop. Counter in Python Jinja Template?

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