How can I check the size of a collection within a Django template?

Question

I have a list in my Django template. I want to do something only if the size of the list is greater than zero.

I have tried myList|length and myList|length_is but they have not been successful.

I've searched all over and don't see any examples. How can I check this?

score 370 · Accepted Answer · edited May 03 '17 at 06:56

370

See https://docs.djangoproject.com/en/stable/ref/templates/builtins/#if : just use, to reproduce their example:

{% if athlete_list %}
    Number of athletes: {{ athlete_list|length }}
{% else %}
    No athletes.
{% endif %}

edited May 03 '17 at 06:56

MichielB

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answered May 23 '09 at 17:53

Alex Martelli

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|length I always get confused with jinja templating in Flask and with django. Thanks for the information. Really helpful. – Doogle Jul 29 '18 at 09:42
18

The `length` filter also seems to work in conditional blocks. e.g. `{% if athlete_list|length > 1 %}...{% endif %}` – Thismatters Sep 08 '18 at 14:05
is there no inline (on lineI) option for that? – Macilias Feb 05 '22 at 13:29

Dave W. Smith · Answer 2 · 2020-10-30T03:37:56.063

128

If you're using a recent Django, changelist 9530 introduced an {% empty %} block, allowing you to write

{% for athlete in athlete_list %}
  ...
{% empty %}
  No athletes
{% endfor %}

Useful when the something that you want to do involves special treatment for lists that might be empty.

edited Oct 30 '20 at 03:37

answered May 24 '09 at 00:35

Dave W. Smith

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Reference: https://docs.djangoproject.com/en/1.9/ref/templates/builtins/#for-empty – Thales Ceolin Jan 25 '16 at 22:41

score 28 · Answer 3 · answered May 23 '09 at 17:52

28

A list is considered to be False if it has no elements, so you can do something like this:

{% if mylist %}
    <p>I have a list!</p>
{% else %}
    <p>I don't have a list!</p>
{% endif %}

answered May 23 '09 at 17:52

mipadi

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score 13 · Answer 4 · answered Apr 15 '11 at 07:31

13

If you tried myList|length and myList|length_is and its not getting desired results, then you should use myList.count

answered Apr 15 '11 at 07:31

Nilesh Tighare

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I'm shocked at how many upvotes this has... If `myList` is a `list` then this calls `list.count()` which raises an error that's masked in the template and gets treated as a false value. The `count` method is to count the number of instances that match the passed in value. However, this works if `myList` is a queryset. – Tim Tisdall Mar 17 '21 at 17:53
Yes, for a collection `|length` can be used. For a QuerySet `.count` is adapted; you could use `exists` as well. – François Constant Apr 25 '23 at 23:47

score 9 · Answer 5 · answered Apr 02 '18 at 06:28

9

You can try with:

{% if theList.object_list.count > 0 %}
    blah, blah...
{% else %}
    blah, blah....
{% endif %}

answered Apr 02 '18 at 06:28

Atarx

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This is just for queryset but not for array length – ilyas Jumadurdyew Feb 26 '22 at 20:34

score 8 · Answer 6 · answered Mar 17 '21 at 18:01

This works:

{% if myList|length %}
    Do something!
{% endif %}

Why there's so many answers here and why there's so much confusion is that this didn't always work. I think at one point template filters couldn't be used on arguments to the if statement and this was later added. It's also now possible to do things such as {% if myList|length >= 3 %}. The filter should do the equivalent of len(myList) so any type of object that can handle that would also be able to handle the |length filter.

nice... had to use `{% if myList|length > 0 %}` (+1) – Tiago Martins Peres Jan 09 '23 at 17:16 — Tiago Martins Peres, Jan 09 '23 at 17:16

score 1 · Answer 7 · answered Mar 11 '19 at 00:45

1

Collection.count no bracket

{% if request.user.is_authenticated %}
{{wishlists.count}}
{% else %}0{% endif %}

answered Mar 11 '19 at 00:45

Ahmed Adewale

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score 1 · Answer 8 · answered Jul 31 '19 at 04:46

I need the collection length to decide whether I should render table <thead></thead>

but don't know why @Django 2.1.7 the chosen answer will fail(empty) my forloop afterward.

I got to use {% if forloop.first %} {% endif %} to overcome:

<table>
    {% for record in service_list %}
        {% if forloop.first %}
            <thead>
            <tr>
                <th>日期</th>
            </tr>
            </thead>
        {% endif %}
        <tbody>
        <tr>
            <td>{{ record.date }}</td>
        </tr>
    {% endfor %}
    </tbody>
</table>

How can I check the size of a collection within a Django template?

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