Django Template - Increment the value of a variable

For increase value in template django: if varint=6, the result will be 8

{{ varint|add:"2" }}

For decrease value in template django:

if varint=6, the result will be 5

  {{ varint|add:"-1" }}

Although this has been answered and goes against what has been said I just had a thought and can't see too much harm if perhaps you made simple counter class like

class Counter:
    count = 0

    def increment(self):
        self.count += 1
        return ''

    def decrement(self):
        self.count -= 1
        return ''

    def double(self):
        self.count *= 2
        return ''

then in your template {{ counter.increment }} {{ counter.count }} etc.

Changing the state of an object in a Django template is discouraged. You should probably bite the bullet, calculate the condition beforehand and pass extra state to the template so you can simplify the template logic.

I'm no purist in this regard by the way, but I have been bitten by the purposeful limitations of Django templates a few times. You're better off not fighting against it, in my opinion.

Being that your intention seems to be to filter out non-matching items, an alternative would be to filter out those in the view and then use {{ forloop.counter }} to sort out the link text you want. So in the view you have something like this:

new_lst = filter(lambda x: x.attr0 == attr0 and x.attr1 == attr1, lst)

And then, in your template:

{% for object in new_lst %}
   <li><a href="{{ object.get_absolute_url }}"> Link {{ forloop.counter }} </a></li>
{% endfor %}