set a variable in django template file, and update it after iteration - django

Question

Trying to set variable in django template, and make a simple rule to update it after iteration. Here is my template:
{% for adv in advs %}
<div class="media-item big" style="top: 18%;left:{% cycle '304' '1078' %}px;">
<div class="media-item__tags">
{{ adv.year }}
{{ adv.payer}}
</div>
<div class="media-item__content">
<div class="media-item__background">
<div class="media-item__canvas">
<div class="media-item__canvas-background" style="background-image: url({{adv.image.url}})"></div>
</div>
<h2 class="topic white upcase fixed-size">{{ adv.name }}</h2>
Смотреть проект
</div>
</div>
</div>
In first div i need to make different 'left:' value. I want to make rule: after every iteration, value changes from base=304 to base+774 px. I tryed to do it somehow with {% cycle %} but it doesnt work for me, also tryed to set variables with {% with %} tag, but didnt find any information about how to update them.

Answer 1

You can set the style by multiplying the current counter from 0...n with 774 and add base value 304. For this, you'll need a custom template tag.
Create a templatetags directory in your app. Add an empty __init__.py and multiply_add.py.
multiply_add.py
from django import template
register = template.Library()
#register.simple_tag
def mul_add(a, b, base_value):
return (a * b) + base_value
template.html
{% load multiply_add %}
{% for adv in advs %}
<div class="media-item big" style="top: 18%;left:{% multiply_add forloop.counter0 774 304 %}px;">
<div class="media-item__tags">
{{ adv.year }}
{{ adv.payer}}
</div>
<div class="media-item__content">
<div class="media-item__background">
<div class="media-item__canvas">
<div class="media-item__canvas-background" style="background-image: url({{adv.image.url}})"></div>
</div>
<h2 class="topic white upcase fixed-size">{{ adv.name }}</h2>
Смотреть проект
</div>
</div>
</div>