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Moved material from django-admin document into a new document, and added new material. Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
112 lines
3.8 KiB
Plaintext
112 lines
3.8 KiB
Plaintext
======================================
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How to provide initial data for models
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======================================
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It's sometimes useful to prepopulate your database with hard-coded data when
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you're first setting up an app. You can provide initial data with migrations or
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fixtures.
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Provide initial data with migrations
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====================================
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To automatically load initial data for an app, create a
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:ref:`data migration <data-migrations>`. Migrations are run when setting up the
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test database, so the data will be available there, subject to :ref:`some
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limitations <test-case-serialized-rollback>`.
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.. _initial-data-via-fixtures:
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Provide data with fixtures
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==========================
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You can also provide data using :ref:`fixtures <fixtures-explanation>`,
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however, this data isn't loaded automatically, except if you use
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:attr:`.TransactionTestCase.fixtures`.
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A fixture is a collection of data that Django knows how to import into a
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database. The most straightforward way of creating a fixture if you've already
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got some data is to use the :djadmin:`manage.py dumpdata <dumpdata>` command.
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Or, you can write fixtures by hand; fixtures can be written as JSON, XML or YAML
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(with PyYAML_ installed) documents. The :doc:`serialization documentation
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</topics/serialization>` has more details about each of these supported
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:ref:`serialization formats <serialization-formats>`.
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.. _PyYAML: https://pyyaml.org/
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As an example, though, here's what a fixture for a ``Person`` model might look
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like in JSON:
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.. code-block:: js
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[
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{
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"model": "myapp.person",
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"pk": 1,
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"fields": {
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"first_name": "John",
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"last_name": "Lennon"
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}
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},
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{
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"model": "myapp.person",
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"pk": 2,
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"fields": {
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"first_name": "Paul",
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"last_name": "McCartney"
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}
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}
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]
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And here's that same fixture as YAML:
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.. code-block:: yaml
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- model: myapp.person
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pk: 1
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fields:
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first_name: John
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last_name: Lennon
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- model: myapp.person
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pk: 2
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fields:
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first_name: Paul
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last_name: McCartney
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You'll store this data in a ``fixtures`` directory inside your app.
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You can load data by calling :djadmin:`manage.py loaddata <loaddata>`
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``<fixturename>``, where ``<fixturename>`` is the name of the fixture file
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you've created. Each time you run :djadmin:`loaddata`, the data will be read
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from the fixture and reloaded into the database. Note this means that if you
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change one of the rows created by a fixture and then run :djadmin:`loaddata`
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again, you'll wipe out any changes you've made.
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Tell Django where to look for fixture files
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-------------------------------------------
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By default, Django looks for fixtures in the ``fixtures`` directory inside each
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app for, so the command ``loaddata sample`` will find the file
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``my_app/fixtures/sample.json``. This works with relative paths as well, so
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``loaddata my_app/sample`` will find the file
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``my_app/fixtures/my_app/sample.json``.
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Django also looks for fixtures in the list of directories provided in the
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:setting:`FIXTURE_DIRS` setting.
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To completely prevent default search form happening, use an absolute path to
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specify the location of your fixture file, e.g. ``loaddata /path/to/sample``.
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.. admonition:: Namespace your fixture files
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Django will use the first fixture file it finds whose name matches, so if
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you have fixture files with the same name in different applications, you
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will be unable to distinguish between them in your ``loaddata`` commands.
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The easiest way to avoid this problem is by *namespacing* your fixture
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files. That is, by putting them inside a directory named for their
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application, as in the relative path example above.
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.. seealso::
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Fixtures are also used by the :ref:`testing framework
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<topics-testing-fixtures>` to help set up a consistent test environment.
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