Django - Pre render signal?

I have a 'live settings' app which I use to store certain global site settings. Certain pages of my site reference these settings, although generally they only use 2-3 at a time. I access these settings using a custom template tag like so:

{% settings site_name %}

Each time I use this tag, the model will retrieve the setting from the database, so if I had something like:

{% settings site_name %} {% settings num_articles %} 

the database would get queried twice.

What I'd like to do is not hit the database more than once per page for the settings values, if I could get all the settings used on a page and then hit the database to retrieve them all, that would be much better.

I had a look thr开发者_C百科ough the documentation and it seems Django has no pre render signal which I could use to update any references to the settings, so does anyone have any suggestions how I could optimise this system? And yes obviously caching is the obvious answer but I'd still like to improve on this for when the page isn't cached.

Agreeing with Daniel that process_template_response is the hook you're looking for. I don't know how many settings you have, but it could also make sense to retrieve all settings once, and store them in some dictionary like structure, so you can access them anytime without hitting the database. You could retrieve them once either per request, or - even if your settings do barely change - when django initializes. You could additionally use django's signals to update your cached settings on delete or update.

If you have a look at django-dbsettings you will see it does a similar thing!

Django 1.3 includes the new TemplateResponse class, which allows you to modify the response later in the rendering process - eg in middleware. This looks like it might do what you want.

If you wish to stick to a scheme similar to what you already have, I'd implement a filter that takes in a list of keys and returns a dict with all the relevant values.

Example filter:

def get_settings(key_list):
    # take values from conf.settings. In practice, can be from any source
    return dict((k, getattr(settings, k, None)) for k in key_list.split(","))
register.filter("get_settings", get_settings)

Usage:

{# load multiple values with a single call #}
{% with "KEY1,KEY2"|get_settings as settings %}
     setting values {{ settings.KEY1 }} and {{ settings.KEY2 }}
{% endwith %}

Note that I used a filter instead of a tag because the with builtin expects a single value before as.