Sum elements of the list in Jinja 2

Question

I have list in Jinja2 that contain dicts in itself. Something like

items = [{'name':'name1', 'points':5}, {'name':'name2', 'points':7}, 
 {'name':'name3', 'points':2}, {'name':'name4', 'points':11}]

What I need is to get sum of all points and to print it somewhere later.

Currently what I got is:

{% set points = 0 -%}
{% for single_item in items -%}
    {% set points = points + single_item["points"] -%}
    {{points}}
{% endfor %}
{{ points }}

Result is: 5 12 14 25 0

Is there any way that I can get that points outside of loop has value 25 (last value from the loop)?

That sort of logic belongs in the controller, not the template. Preprocess your data accordingly, and pass `items` as tell as `total` to the template. — Lukas Graf, Aug 27 '14 at 10:47
@LukasGraf I agree with you totally, but in my case, it would make big mess. — Perun, Aug 27 '14 at 11:17

score 47 · Answer 1 · edited Jul 09 '21 at 08:17

47

Jinja2 includes a sum filter which will do this for you:

{{ items | sum(attribute='points') }}

See documentation here: https://jinja.palletsprojects.com/templates/#jinja-filters.sum

edited Jul 09 '21 at 08:17

HackDolphin

166
11

answered Oct 27 '16 at 15:54

Bartlett

844
6
9

4

this should be the accepted answer. Cleaner than the accepted answer but still does work as it should – TheWhiteLlama Jun 30 '17 at 18:40

score 3 · Answer 2 · answered Aug 27 '14 at 11:03

That sort of logic should usually go in the controller, not the template (separating logic from presentation). Preprocess your data accordingly, and pass items as well as total to the template:

from jinja2 import Template

template = Template(open('index.html').read())

items = [{'name': 'name1', 'points': 5},
         {'name': 'name2', 'points': 7},
         {'name': 'name3', 'points': 2},
         {'name': 'name4', 'points': 11}]

total = sum([i['points'] for i in items])

print template.render(items=items, total=total)

index.html:

<table>

{% for item in items %}
  <tr>
    <td>{{ item.name }}</td>
    <td>{{ item.points }}</td>
  </tr>
{% endfor %}

</table>

<strong>Total:</strong>{{ total }}

For details on the expression sum([i['points'] for i in items]) see list comprehensions.

Although this is good answer, and I know it can be done this way, for my case it won't work well. Will have several dictionaries with supporting values, and have total mess of code. I think I've found a way how to do this, need to test it bit more, and if it is working, will post answer. — Perun, Aug 27 '14 at 11:16
Then you probably need to refactor your code. Can you edit your question to include an example of your code and several dictionaries? — Lukas Graf, Aug 27 '14 at 11:20

score 3 · Accepted Answer · answered Aug 27 '14 at 12:56

3

I've managed to make it work, although solution is not elegant, but it is working:

{% set points = [0] -%}
{% for single_item in items -%}
    {% if points.append(points.pop()+ single_item["points"]) -%}{% endif %}
{% endfor %}
{{ points }}

points will be array with just one element that has sum.

It can be also done with included do extension, and that would replace {% if %} line.

answered Aug 27 '14 at 12:56

Perun

217
1
2
7

1

This is not the best answer – caspii May 26 '21 at 20:55

score -1 · Answer 4 · answered Oct 06 '22 at 11:12

Found on: https://linuxtut.com/en/129012d5539a8724556d/

Solution 2: Use namespace <2019/12/21: From na90ya> It seems that variables are preserved when using namespace objects introduced in 2.10 of jinja2. (Reference material [1])

count_test3.j2

{%- set ns = namespace(cnt=1) -%}
{%- for i in range(3) -%}
{%- set ns.cnt = ns.cnt + 1 -%}
{{ ns.cnt }}
{% endfor -%}
result : {{ ns.cnt }}

But i didn't try it yet...

Sum elements of the list in Jinja 2

4 Answers4

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