If you've ever wanted to dynamically lookup values in the template layer (e.g. `dictionary[bar]`), then you've probably realized/been told to do this in the python layer. The problem is then you often to build a huge 2-D list to hold all of that data.
These are two solutions to this problem: by using generators we can be lazy while still making it easy in the python layer. I'm going to write more documentation later, but here's a quick example:
from lazy_lookup import lazy_lookup_dict
def some_view(request):
users = User.objects.values('id', 'username')
articles = Article.objects.values('user', 'title', 'body')
articles = dict([(x['user'], x) for x in articles])
return render_to_response('some_template.html',
{'data': lazy_lookup_dict(users, key=lambda x: x['id'],
article=articles,
item_name='user')})
Then in the template layer you'd write something like:
{% for user_data in data %}
{{ user_data.user.username }}, {{ user_data.article.title }}
{% endfor %}
- template
- dynamic
- lookup
- lazy
- dynamic-lookup
Have you ever felt the need to run multiple Django projects on the same memcached server? How about other cache backends? To scope the cache keys, you simply need to prefix. However, since a lot of Django's internals rely on `django.core.cache.cache`, you cannot easily replace it everywhere.
This will automatically upgrade the `django.core.cache.cache` object if `settings.CACHE_PREFIX` is set to a string and the Middleware contains `ScopeCacheMiddleware`.
A thread discussing the merging of this functionality into Django is available on [the dev mailing list](http://groups.google.com/group/django-developers/browse_thread/thread/d45edaafec56da2a).
However, (as of now) nowhere in the thread does anyone mention the reason why this sort of treatment is needed: Many of Django's internal caching helpers use `django.core.cache.cache`, and will then conflict if multiple sites run on the same cache stores.
Example Usage:
>>> from django.conf import settings
>>> from django.core.cache import cache
>>> from scoped_caching import prefix_cache_object
>>> settings.CACHE_PREFIX
'FOO_'
# Do this once a process (e.g. on import or Middleware)
>>> prefix_cache_object(settings.CACHE_PREFIX, cache)
>>> cache.set("pi", 3.14159)
>>> cache.get("pi")
3.14159
>>> cache.get("pi", use_global_namespace=True)
>>> cache.get("FOO_pi", use_global_namespace=True)
3.14159
>>> cache.set("FOO_e", 2.71828, use_global_namespace=True)
>>> cache.get("e")
2.71828
To Install: Simply add `ScopeCacheMiddleware` as a middleware and define `settings.CACHE_PREFIX` and enjoy!
- middleware
- cache
- namespace