Set variable in jinja

Question

I would like to know how can I set a variable with another variable in jinja. I will explain, I have got a submenu and I would like show which link is active. I tried this:

{% set active_link = {{recordtype}} -%}

where recordtype is a variable given for my template.

Folks landing here from Google: you will probably be primarily interested in the [official docs on the `set` tag](http://jinja.pocoo.org/docs/latest/templates/#assignments), rather than the specific syntax mistake made by the asker here or how to fix it, which is what the top answers here and at the linked duplicate address. — Mark Amery, Mar 03 '19 at 20:33

Soviut · Answer 1 · 2013-08-29T19:39:36.000

663

{{ }} tells the template to print the value, this won't work in expressions like you're trying to do. Instead, use the {% set %} template tag and then assign the value the same way you would in normal python code.

{% set testing = 'it worked' %}
{% set another = testing %}
{{ another }}

Result:

it worked

edited Aug 29 '13 at 19:39

answered Nov 15 '10 at 05:18

Soviut

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if my variable is dict what now {% set dict.key = 'test' %} don't work – Ib33X Nov 11 '11 at 11:19
A deleted answer also included this link, which serves as supplementary information to this answer: http://jinja.pocoo.org/docs/tricks/#highlighting-active-menu-items – Pascal Jul 12 '16 at 07:37
can we create a global jinja variable and use it throughout the html file in which we embed the jinja variable? @Soviut – Sri Test Jun 19 '20 at 12:48
To further illustrate by extending this example: `{% set another = testing + " flawlessly" %}` `{{ another }}` Result: `it worked flawlessly` – LunkRat Jul 01 '22 at 15:14
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@LunkRat It is recommended to use `~` to concatenate strings, rather than `+` (see https://jinja.palletsprojects.com/en/2.11.x/templates/#math) – Jean-Francois T. Jan 28 '23 at 07:49

score 93 · Answer 2 · answered Oct 21 '16 at 12:57

93

Nice shorthand for Multiple variable assignments

{% set label_cls, field_cls = "col-md-7", "col-md-3" %}

answered Oct 21 '16 at 12:57

pymen

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This doesn't seem to come close to answering the question? – John R Perry Aug 21 '19 at 19:00
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@JohnRPerry But it is a nice addition to the accepted answer. – Meet Sinojia Nov 23 '20 at 06:53

score 30 · Answer 3 · answered Sep 09 '14 at 19:56

30

Just Set it up like this

{% set active_link = recordtype -%}

answered Sep 09 '14 at 19:56

Chad Pierce

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Why specifically like so (the minus sign at the end but not at the beginning)? This would remove trailing but not leading whitespace, if I am not mistaken. To what end? – Leonid Nov 07 '16 at 06:00
29

Its in the original question ¯\\_(ツ)_/¯ – Graham P Heath Apr 25 '18 at 19:05
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The minus sign - appended to either the start or end of a statement (e.g. {%- -%}) tells Jinja to strip the new line that follows it. see https://www.webforefront.com/django/usebuiltinjinjastatements.html – Gevorg Hakobyan Jul 01 '21 at 11:38

score 16 · Answer 4 · answered May 15 '22 at 14:10

You can do this with the set tag. See the official documentation.

For example,

{% set foo = "bar" %}
{{ foo }}

outputs

bar

Note: there are scoping issues which means that variable values don’t persist between loop iterations, for example, if you want some output to be conditional on a comparison between previous and current loop values:

{# **DOES NOT WORK AS INTENDED** #}

{% set prev = 0 %}
{% for x in [1, 2, 3, 5] %}
{%- if prev != x - 1 %}⋮ (prev was {{ prev }})
{% endif -%}
{{ x }}
{%- set prev = x %}
{% endfor %}

prints

1
⋮ (prev was 0)
2
⋮ (prev was 0)
3
⋮ (prev was 0)
5

because the variable isn’t persisted. Instead you can use a mutable namespace wrapper:

{% set ns = namespace(prev=0) %}
{% for x in [1, 2, 3, 5] %}
{%- if ns.prev != x - 1 %}⋮ (ns.prev was {{ ns.prev }})
{% endif -%}
{{ x }}
{%- set ns.prev = x %}
{% endfor %}

which prints

1
2
3
⋮ (ns.prev was 3)
5

as intended.

Set variable in jinja

4 Answers4

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