A Django Template tag to create or reuse all node of the template (with memcache)

gistfile1.py

import logging

from google.appengine.api import memcache

from django.conf import settings
from django import template


class HTMLListNode (template.Node):
    """ Create or reuse all node of the template.                                                                                                                                 
                                                                                                                                                                                                       
    For each node generated by the template, the data are added into memcache                                                                                                                          
    If the node into memcache is always valid it will be reused.                                                                                                                                       
                                                                                                                                                                                                       
    Example:                                                                                                                                                                                           
                                                                                                                                                                                                       
      Before:                                                                                                                                                                                          
      That is bad because, need to make for each node a request to memcache one by one.                                                                                                                
                                                                                                                                                                                                       
      {% for item in object_list %}                                                                                                                                                                    
        {% cache 9800 item.login item.updated %}                                                                                                                                                       
          {% include "templates/block.html" %}                                                                                                                                                         
        {% endcache%}                                                                                                                                                                                  
      {% endfor %}                                                                                                                                                                                     
                                                                                                                                                                                                       
      After:                                                                                                                                                                                           
      That use the method get_multi and set_multi from memcache.                                                                                                                                       
                                                                                                                                                                                                       
      {% html_list request, items.object_list, "templates/block.html" "%(login)s %(updated)s" %}                                                                                                       
    """
    def __init__(self, request, items, path, cache):
        self.request      = template.Variable (request)
        self.items        = template.Variable (items)
        self.path         = template.Variable (path)
        self.cache        = template.Variable (cache)

    def render (self, context):
        request = self.request.resolve (context)
        items = self.items.resolve (context)
        path  = unicode (self.path.resolve (context))
        cache = unicode (self.cache.resolve (context))

        template_cache = path + "." + cache

        data_keys = [template_cache % x for x in items]
        data_cached = memcache.get_multi (data_keys)
        data_notcached = {}

        c = template.RequestContext (request, locals ())
        t = template.loader.get_template (path)

        result = []
        for item in items:
            k = template_cache % item
            if data_cached.has_key (k):
                result.append (data_cached[k])
            else:
                c['item'] = item
                data_notcached[k] = t.render (c)
                result.append (data_notcached[k])

        if data_notcached:
            memcache.set_multi (data_notcached)

        return "".join (result)

def do_list (parser, token):
    try:
        tag_name, request, items, template_path, cache = token.split_contents ()
    except ValueError:
        raise template.TemplateSyntaxError, "%r tag requires a 4 arguments" % token.contents.split ()[0]
    return HTMLListNode (request, items, template_path, cache)
register.tag ('html_list', do_list)