django/docs/faq/usage.txt

FAQ: Using Django
=================

Why do I get an error about importing DJANGO_SETTINGS_MODULE?
-------------------------------------------------------------

Make sure that:

* The environment variable DJANGO_SETTINGS_MODULE is set to a
  fully-qualified Python module (i.e. "mysite.settings").

* Said module is on ``sys.path`` (``import mysite.settings`` should work).

* The module doesn't contain syntax errors (of course).

* If you're using mod_python but *not* using Django's request handler,
  you'll need to work around a mod_python bug related to the use of
  ``SetEnv``; before you import anything from Django you'll need to do
  the following::

        os.environ.update(req.subprocess_env)

  (where ``req`` is the mod_python request object).

I can't stand your template language. Do I have to use it?
----------------------------------------------------------

We happen to think our template engine is the best thing since chunky bacon,
but we recognize that choosing a template language runs close to religion.
There's nothing about Django that requires using the template language, so
if you're attached to ZPT, Cheetah, or whatever, feel free to use those.

Do I have to use your model/database layer?
-------------------------------------------

Nope. Just like the template system, the model/database layer is decoupled from
the rest of the framework.

The one exception is: If you use a different database library, you won't get to
use Django's automatically-generated admin site. That app is coupled to the
Django database layer.

How do I use image and file fields?
-----------------------------------

Using a :class:`~django.db.models.FileField` or an
:class:`~django.db.models.ImageField` in a model takes a few steps:

#. In your settings file, you'll need to define :setting:`MEDIA_ROOT` as
   the full path to a directory where you'd like Django to store uploaded
   files. (For performance, these files are not stored in the database.)
   Define :setting:`MEDIA_URL` as the base public URL of that directory.
   Make sure that this directory is writable by the Web server's user
   account.

#. Add the :class:`~django.db.models.FileField` or
   :class:`~django.db.models.ImageField` to your model, making sure to
   define the :attr:`~django.db.models.FileField.upload_to` option to tell
   Django to which subdirectory of :setting:`MEDIA_ROOT` it should upload
   files.

#. All that will be stored in your database is a path to the file
   (relative to :setting:`MEDIA_ROOT`). You'll most likely want to use the
   convenience :attr:`~django.core.files.File.url` attribute provided by
   Django. For example, if your :class:`~django.db.models.ImageField` is
   called ``mug_shot``, you can get the absolute path to your image in a
   template with ``{{ object.mug_shot.url }}``.

How do I make a variable available to all my templates?
-------------------------------------------------------

Sometimes your templates just all need the same thing. A common example would
be dynamically-generated menus. At first glance, it seems logical to simply
add a common dictionary to the template context.

The correct solution is to use a ``RequestContext``. Details on how to do this
are here: :ref:`subclassing-context-requestcontext`.