How can explicitly reset a template fragment cache in Django?

Question

I am using Memcache for my Django application.

In Django, developers can use template fragment caching to only cache a section of a template. https://docs.djangoproject.com/en/dev/topics/cache/#template-fragment-caching

I was wondering if there is a way to explicitly change the value of a template fragment cache section say in views.py. For instance, could one use a method akin to cache.set("sidebar", "new value") except for a template fragment cache?

Thank you for your help.

Answer 1

In theory, yes. You first have to create a template cache key in the same pattern used by Django, which can be done with this snippet of code:

from django.utils.hashcompat import md5_constructor
from django.utils.http import urlquote

def template_cache_key(fragment_name, *vary_on):
    """Builds a cache key for a template fragment.

    This is shamelessly stolen from Django core.
    """
    base_cache_key = "template.cache.%s" % fragment_name
    args = md5_constructor(u":".join([urlquote(var) for var in vary_on]))
    return "%s.%s" % (base_cache_key, args.hexdigest())

You could then do something like cache.set(template_cache_key(sidebar), 'new content') to change it.

However, doing that in a view is kind of ugly. It makes more sense to set up post-save signals and expire cache entries when models change.

^{The above code snippet works for Django 1.2 and below. I'm not sure about Django 1.3+ compatibility; django/templatetags/cache.py will have the latest info.}

^{For Django 1.7, django/core/cache/utils.py has a usable function.}