Django slice variable in template

Question

I am trying to cut a slice a list of images to split them over a few pages of a pdf I am generating. But im not sure what the syntax I need to use is. (or if there is a better way).

 {% for page in image_pages %} // range loop for number of pages (passed from view)
    <p style="page-break-before: always"></p> // new page break for each page
    <div class="img-wrapper">
        {% for image in project_images|slice:"0:12" %}
             <div class="img-box" style="margin: 5px">
                <img
                  class="report-img"
                  src="{{ base_url }}{{ image.path.url }}"
                />
             </div>
        {% endfor %}
    </div>

{% endfor %}

What i want to do is adjust this line

  {% for image in project_images|slice:"0:12" %}

To something like (to print 12 images from total image list sent)

  {% for image in project_images|slice:"page*12:page*12+12" %}

nigel222 · Accepted Answer · 2022-11-30T15:11:20.713

You could write your own template tag to slice with variable arguments. The Django-supplied template engine doesn't include this. The authors believe that the right place to do this sort of thing is in the Python code. Something like

display = []
for page in image_pages:
    display.append([
        page, 
        project_images[page*12:page*12+12]
    ])
context['display'] = display

And the template then becomes

{% for page, image_list in display %}
    <p style="page-break-before: always"></p> // new page break for each page
    <div class="img-wrapper">
    {% for image in image_list %}
         <div class="img-box" style="margin: 5px">
            <img
              class="report-img"
              src="{{ base_url }}{{ image.path.url }}"
            />
         </div>
    {% endfor %}
</div>
{% endfor %}

The other option is to use Jinja instead of the Django template engine.

I just worked out the working in the answer I posted. Your way of doing in the view makes more sense though. I will implement and report back. Thank you. — Spirconi, Nov 30 '22 at 14:12

score 0 · Answer 2 · answered Nov 30 '22 at 14:10

Along with this answer i did the below to achieve what i needed. https://stackoverflow.com/a/23783666/14143473. I also used https://pypi.org/project/django-mathfilters/

 {% for page in image_pages %}
       <p style="page-break-before: always"></p>
       {% with start=page|mul:12 end=page|mul:12|add:12 %}
       
            {% with start|addstr:":"|addstr:end as imageSlice %}
           
              <div class="img-wrapper">
                {% for image in project_images|slice:imageSlice %}
                <div class="img-box" style="margin: 5px">
                  <img
                    class="report-img"
                    src="{{ base_url }}{{ image.path.url }}"
                  />
                </div>
                {% endfor %}
              </div>
          

            {% endwith %}
  
       {% endwith %} 
{% endfor %}

Django slice variable in template

2 Answers2