update value of a variable inside a template - django

Question

I have seen enough number of examples that allow me to declare a new variable inside a template and set its value. But what I want to do is to update the value of a particular variable inside the template.

For example I have a datetime field for an object and I want to add timezone according to the request.user from the template. So I will create a template filter like {% add_timezone object.created %} and what it will do is that it will add timezone to object.created and after that whenever I access {{object.created}} it will give me the updated value.

Can anybody tell me how this can be done. I know I need to update the context variable from the template filter. But don't know how.

Answer 1

You cannot modify a value in a template, but you can define 'scope' variables using the {% with %} tag:

{% with created=object.created|add_timezone %}
    Date created with fixed timezone: {{ created }}
{% endwith %}

where add_timezone is a simple filter:

def add_timezone(value):
    adjusted_tz = ...
    return adjusted_tz

register.filter('add_timezone', add_timezone)