django1/docs/howto/initial-data.txt

=================================
Providing initial data for models
=================================

It's sometimes useful to pre-populate your database with hard-coded data when
you're first setting up an app. You can provide initial data with migrations or
fixtures.

Providing initial data with migrations
======================================

If you want to automatically load initial data for an app, create a
:ref:`data migration <data-migrations>`. Migrations are run when setting up the
test database, so the data will be available there, subject to :ref:`some
limitations <test-case-serialized-rollback>`.

.. _initial-data-via-fixtures:

Providing data with fixtures
============================

You can also provide data using fixtures, however, this data isn't loaded
automatically, except if you use :attr:`.TransactionTestCase.fixtures`.

A fixture is a collection of data that Django knows how to import into a
database. The most straightforward way of creating a fixture if you've already
got some data is to use the :djadmin:`manage.py dumpdata <dumpdata>` command.
Or, you can write fixtures by hand; fixtures can be written as JSON, XML or YAML
(with PyYAML_ installed) documents. The :doc:`serialization documentation
</topics/serialization>` has more details about each of these supported
:ref:`serialization formats <serialization-formats>`.

.. _PyYAML: https://www.pyyaml.org/

As an example, though, here's what a fixture for a simple ``Person`` model might
look like in JSON:

.. code-block:: js

    [
      {
        "model": "myapp.person",
        "pk": 1,
        "fields": {
          "first_name": "John",
          "last_name": "Lennon"
        }
      },
      {
        "model": "myapp.person",
        "pk": 2,
        "fields": {
          "first_name": "Paul",
          "last_name": "McCartney"
        }
      }
    ]

And here's that same fixture as YAML:

.. code-block:: yaml

    - model: myapp.person
      pk: 1
      fields:
        first_name: John
        last_name: Lennon
    - model: myapp.person
      pk: 2
      fields:
        first_name: Paul
        last_name: McCartney

You'll store this data in a ``fixtures`` directory inside your app.

Loading data is easy: just call :djadmin:`manage.py loaddata <loaddata>`
``<fixturename>``, where ``<fixturename>`` is the name of the fixture file
you've created. Each time you run :djadmin:`loaddata`, the data will be read
from the fixture and re-loaded into the database. Note this means that if you
change one of the rows created by a fixture and then run :djadmin:`loaddata`
again, you'll wipe out any changes you've made.

Where Django finds fixture files
--------------------------------

By default, Django looks in the ``fixtures`` directory inside each app for
fixtures. You can set the :setting:`FIXTURE_DIRS` setting to a list of
additional directories where Django should look.

When running :djadmin:`manage.py loaddata <loaddata>`, you can also
specify a path to a fixture file, which overrides searching the usual
directories.

.. seealso::

    Fixtures are also used by the :ref:`testing framework
    <topics-testing-fixtures>` to help set up a consistent test environment.