django-constance 0.3

Django live settings with pluggable backends, including Redis.

Features

• Easily migrate your static settings to dynamic settings.

• Admin interface to edit the dynamic settings.

Installation

Install from PyPI:

pip install django-constance

Or install the in-development version using pip:

pip install -e git+git://github.com/comoga/django-constance#egg=django-constance

Configuration

Modify your settings.py. Add 'constance' to your INSTALLED_APPS, and move each key you want to turn dynamic into the CONSTANCE_CONFIG section, like this:

INSTALLED_APPS = (
    ...
    'constance',
)

CONSTANCE_CONFIG = {
    'MY_SETTINGS_KEY': (42, 'the answer to everything'),
}

Here, 42 is the default value for the key MY_SETTINGS_KEY if it is not found in the backend. The other member of the tuple is a help text the admin will show.

See the Backends section how to setup the backend.

Backends

Constance ships with a bunch of backends that are used to store the configuration values. By default it uses the Redis backend. To override the default please set the CONSTANCE_BACKEND setting to the appropriate dotted path.

Redis (default)

CONSTANCE_BACKEND = constance.backends.redisd.RedisBackend

The is the default backend and has a couple of options:

• CONSTANCE_REDIS_CONNECTION

  A dictionary of parameters to pass to the to Redis client, e.g.:

  CONSTANCE_REDIS_CONNECTION = {
      'host': 'localhost',
      'port': 6379,
      'db': 0,
  }

• CONSTANCE_REDIS_CONNECTION_CLASS

  An (optional) dotted import path to a connection to use, e.g.:

  CONSTANCE_REDIS_CONNECTION_CLASS = 'myproject.myapp.mockup.Connection'

• CONSTANCE_REDIS_PREFIX

  The (optional) prefix to be used for the key when storing in the Redis database. Defaults to 'constance:'. E.g.:

  CONSTANCE_REDIS_PREFIX = 'constance:myproject:'

Database

CONSTANCE_BACKEND = constance.backends.database.DatabaseBackend

If you want to use this backend you also need to add the databse backend to your INSTALLED_APPS setting to make sure the data model is correctly created:

INSTALLED_APPS = (
    # other apps
    'constance.backends.database',
)

It also uses django-picklefield to store the values in the database, so you need to install this library, too. E.g.:

pip install django-picklefield

The database backend has the ability to automatically cache the config values and clear them when saving. You need to set the following setting to enable this feature:

CONSTANCE_DATABASE_CACHE_BACKEND = 'memcached://127.0.0.1:11211/'

Note

This won’t work with a cache backend that doesn’t support cross-process caching, because correct cache invalidation can’t be guaranteed.

Usage

Constance can be used from your Python code and from your Django templates.

• Python

  Accessing the config variables is as easy as importing the config object and accessing the variables with attribute lookups:

  from constance import config
  
  # ...
  
  if config.MY_SETTINGS_KEY == 42:
      answer_the_question()

• Django templates

  To access the config object from your template, you can either pass the object to the template context:

  from django.shortcuts import render_to_response
  from constance import config
  
  def myview(request):
      return render_to_response('my_template.html', {'config': config})

  Or you can use the included config context processor.:

  TEMPLATE_CONTEXT_PROCESSORS = (
      # ...
      'constance.context_processors.config',
  )

  This will add the config instance to the context of any template rendered with a RequestContext.

  Then, in your template you can refer to the config values just as any other variable, e.g.:

  <h1>Welcome on {% config.SITE_NAME %}</h1>
  {% if config.BETA_LAUNCHED %}
      Woohoo! Head over <a href="/sekrit/">here</a> to use the beta.
  {% else %}
      Sadly we haven't launched yet, click <a href="/newsletter/">here</a>
      to signup for our newletter.
  {% endif %}

Editing

Fire up your admin and you should see a new app called Constance with MY_SETTINGS_KEY in the Config pseudo model.

Screenshots

The standard edit screen.

The virtual application Constance among your regular applications.