Django - Generic Custom Model Manager for summarizing data by any field

1-models.py

''' 
This Snippet, lets you create a generic custom model manager to summarize data on a table by any field. 

Benefits: 
- You wont be repeating yourself! 
- A single url & template can be used to summarize by any field in your model

Example Usage:  Book.counts.by(field, year, month, day) i.e Book.counts.by(category, 2009, 9, 24)

Notes: 
- day is optional 
- My current use case only requires summaries by month/day, this snippet could easily be modified to make both month and year optional using **kwargs

Instructions:
1. Create your custom model manager & assign it to your model (models.py)
2. Create your view (views.py)
3. Add urls (urls.py) 
4. Create a new template tag and register it (get.py)
5. Customize your template

'''
from django.db import models
from django.db.models import Count 

# Snippet for your models.py
class CountsManager(models.Manager):
    def by(self, field, year, month, *args):
        year = year
        month = month
        field = field
        if args:
            day = args[0]
            return self.filter(pub_date_time__year=year).filter(pub_date_time__month=month).filter(pub_date_time__day=day).values(field).annotate(Count(field))
        else:
            return self.filter(pub_date_time__year=year).filter(pub_date_time__month=month).values(field).annotate(Count(field))

# Add the custom manager to your model
class Book(models.Model):
	pub_date_time = models.DateTimeField(blank=True, null=True)
	author = models.CharField(max_length=50,blank=True, null=True)
	publisher = models.CharField(max_length=50,blank=True, null=True)
	category = models.CharField(max_length=50,blank=True, null=True)

	
	objects = models.Manager()
	counts = CountsManager()

2-views.py

from django.views.generic.list_detail import object_list
from myproject.app.models import Book

# Snippet for your views.py
def by(request, field, year , month, **kwargs):
    field = field
    field_count = field + "__count"
    context = {'year': year, 'month': month, 'field': field, 'field_count': field_count}
    if kwargs:
        day = kwargs['day']
        query = Book.counts.by(field, year, month, day)
        context['day'] = day
    else:
        query = Book.counts.by(field, year, month)
    template = 'type.html'
    return object_list(request,
                    queryset=query,
                    template_name = template,
                    extra_context = context
)
 

3-urls.py

from django.conf.urls.defaults import *

# Snippet for your urls.py
 
urlpatterns = patterns('myapp.views',
    url('^(?P<field>[\w-]+)/(?P<year>\d{4})/(?P<month>\d+)/$','by', name='count_link_month'),
    url('^(?P<field>[\w-]+)/(?P<year>\d{4})/(?P<month>\d+)/(?P<day>\d+)/$','by', name='chart_link_day'),
)

4-get.py

from django.template import Library

register = Library()

# Add the following filter in your templatetags dir - Source: http://www.djangosnippets.org/snippets/1412/

@register.filter
def get( dict, key, default = '' ):
  """
  Usage:

  view:
  some_dict = {'keyA':'valueA','keyB':{'subKeyA':'subValueA','subKeyB':'subKeyB'},'keyC':'valueC'}
  keys = ['keyA','keyC']
  template:
  {{ some_dict|get:"keyA" }}
  {{ some_dict|get:"keyB"|get:"subKeyA" }}
  {% for key in keys %}{{ some_dict|get:key }}{% endfor %}
  """

  try:
    return dict.get(key,default)
  except:
    return default + 'Except Clause'

5-template.html

<--  Make your template generic by using the two variables (field & field__count) passed in the context variable customize the code below for your template template -->
{% for object in object_list %}
<h1>{{ object|get:field }} : {{ object|get:field_count }}</h1>
{% endfor %}