Get lengths of a list in a jinja2 template

Question

How do I get the number of elements in a list in jinja2 template?

For example, in Python:

print(template.render(products=[???]))

and in jinja2

<span>You have {{what goes here?}} products</span>

score 797 · Accepted Answer · edited Mar 05 '17 at 21:39

797

<span>You have {{products|length}} products</span>

You can also use this syntax in expressions like

{% if products|length > 1 %}

jinja2's builtin filters are documented here; and specifically, as you've already found, length (and its synonym count) is documented to:

Return the number of items of a sequence or mapping.

So, again as you've found, {{products|count}} (or equivalently {{products|length}}) in your template will give the "number of products" ("length of list")

edited Mar 05 '17 at 21:39

tshepang

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answered Sep 23 '09 at 14:55

Alex Martelli

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Can we check for undefined too? I have to use {% if products is none ... %} which is quite tiring – Nam G VU Aug 21 '17 at 04:28
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@wvxvw this does work: `{% set item_count = items | length %}` as long as `items` is a list, dict, etc. – kbolino May 14 '19 at 17:51
Thanks @AlexMartelli. In addition we could use inline syntax like `{{ form.select_field(size=5 if form.select_field.choices|count > 5 else form.select_field.choices|count) }}` – Filipe Bezerra de Sousa Jun 28 '20 at 23:52

score 16 · Answer 2 · answered Sep 22 '16 at 10:13

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Alex' comment looks good but I was still confused with using range. The following worked for me while working on a for condition using length within range.

{% for i in range(0,(nums['list_users_response']['list_users_result']['users'])| length) %}
<li>    {{ nums['list_users_response']['list_users_result']['users'][i]['user_name'] }} </li>
{% endfor %}

answered Sep 22 '16 at 10:13

Ashwin

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You can loop through your collection in pythonic way: ```{% for user in nums['list_users_response']['list_users_result']['users'] %}
{{ user['user_name'] }}

dmitry_romanov

Jul 04 '21 at 10:48

score 6 · Answer 3 · answered Jul 04 '19 at 21:26

6

I've experienced a problem with length of None, which leads to Internal Server Error: TypeError: object of type 'NoneType' has no len()

My workaround is just displaying 0 if object is None and calculate length of other types, like list in my case:

{{'0' if linked_contacts == None else linked_contacts|length}}

answered Jul 04 '19 at 21:26

Dmitri

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You could use **none** build-in function to test for _None_. Check more here: [https://jinja.palletsprojects.com/en/2.10.x/templates/#none](https://jinja.palletsprojects.com/en/2.10.x/templates/#none). Example is on this thread: [https://stackoverflow.com/questions/19614027/jinja2-template-variable-if-none-object-set-a-default-value](https://stackoverflow.com/questions/19614027/jinja2-template-variable-if-none-object-set-a-default-value) – Wojciech Jakubas Dec 17 '19 at 16:50

score 5 · Answer 4 · answered Jan 02 '22 at 06:21

5

If for loop with array is used then you can use the following

{% for i in range(array|length) %}
          array[i]
{% endfor %}

answered Jan 02 '22 at 06:21

Ali Hussein

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score 0 · Answer 5 · answered Aug 30 '23 at 05:16

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Try it:

<span>You have {% for n in products %}{% if loop.index == 1 %}{{ loop.length }}{% endif %}{% endfor %} products</span>

answered Aug 30 '23 at 05:16

Abolfazl Rastgou

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Get lengths of a list in a jinja2 template

5 Answers5

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