Jinja provides two types of loops. The first one is the for loop:
Loop over each item in an array. For example, to display a list of users given user_list:
<ul>
{% for user in user_list %}
<li><a href="/profile/{{ user.id }}/">{{ user.name }}</a></li>
{% endfor %}
</ul>
You can also loop over a list in reverse by using {% for obj in list reversed %}.
You can also define a {% elsefor %} statement, which gets rendered if the for loop doesn't iterate:
<ul>
{% for user in userlist %}
<li>{{ user }}</li>
{% elsefor %}
<li><strong>no user found</strong></li>
{% endfor %}
</ul>
range loops can be used to iterate through a list of numbers:
{% range number from 1 to 10 %}
{{ number }}
{% endrange %}
You can also step downwards:
{% range number from 10 downto 1 %}
{{ number }}
{% endrange %}
It is even possible to set the stepsize:
{% range number from 1 to 100 step 33 %}
{{ number }}
{% endrange %}
These variables are available inside each for and range loop:
| Variable | Description |
|---|---|
| loop.counter | The current iteration of the loop |
| loop.counter0 | The current iteration of the loop, starting counting by 0. |
| loop.revcounter | The number of iterations from the end of the loop. |
| loop.revcounter0 | The number of iterations from the end of the loop, starting counting by 0. |
| loop.first | True if first iteration. |
| loop.last | True if last iteration. |
| loop.even | True if current iteration is even. |
| loop.odd | True if current iteration is odd. |
| loop.parent | The context of the parent loop. |
Cycle among the given strings each time this tag is encountered.
Within a loop, cycles among the given strings each time through the loop:
{% for row in rows %}
<tr class="{% cycle 'row1', 'row2' inline %}">
...
</tr>
{% endfor %}
Or by cycling into a variable:
{% for row in rows %}
{% cycle rowclass through "row1", "row2" %}
<tr>
<td class="{{ rowclass }}">...</td>
<td class="{{ rowclass }}">...</td>
...
</tr>
{% endfor %}
Check if a value has changed from the last iteration of a loop.
The 'ifchanged' block tag is used within a loop. It checks its own rendered contents against its previous state and only displays its content if the value has changed:
<h1>Userlist</h1>
{% for user in users %}
{% ifchanged %}<h3>{{ user.type }}</h3>{% endifchanged %}
{{ user.name }}
{% endfor %}
Often it's important to be able to use recursion. For example when you want to build a sitemap or a tree.
In Jinja every for tag can be used to call it again with other variables:
<ul class="sitemap">
{% for item in sitemap %}
<li><a href="{{ item.link }}">{{ item.title|e }}</a>{%
if item.items %}<ul>{% recurse item.items %}</ul></li>
{% endfor %}
</ul>
If you want to recurse in a higher loop you can use this syntax:
{% recurse item.items in loop.parent %}