Loading initial data with Django 1.7 and data migrations
I recently switched from Django 1.6 to 1.7, and I began using migrations (I never used South).
Before 1.7, I used to load initial data with a
fixture/initial_data.json file, which was loaded with the
python manage.py syncdb command (when creating the database).
Now, I started using migrations, and this behavior is deprecated :
If an application uses migrations, there is no automatic loading of fixtures. Since migrations will be required for applications in Django 2.0, this behavior is considered deprecated. If you want to load initial data for an app, consider doing it in a data migration. (https://docs.djangoproject.com/en/1.7/howto/initial-data/#automatically-loading-initial-data-fixtures)
The official documentation does not have a clear example on how to do it, so my question is :
What is the best way to import such initial data using data migrations :
- Write Python code with multiple calls to
- Use or write a Django function (like calling
loaddata) to load data from a JSON fixture file.
I prefer the second option.
I don't want to use South, as Django seems to be able to do it natively now.
Update : See @GwynBleidD's comment below for the problems this solution can cause, and see @Rockallite's answer below for an approach that's more durable to future model changes.
Assuming you have a fixture file in
- Create your empty migration:
In Django 1.7:
python manage.py makemigrations --empty <yourapp>
In Django 1.8+, you can provide a name:
python manage.py makemigrations --empty <yourapp> --name load_intial_data
- Edit your migration file
2.1. Custom implementation, inspired by Django'
loaddata (initial answer):
import os from sys import path from django.core import serializers fixture_dir = os.path.abspath(os.path.join(os.path.dirname(__file__), '../fixtures')) fixture_filename = 'initial_data.json' def load_fixture(apps, schema_editor): fixture_file = os.path.join(fixture_dir, fixture_filename) fixture = open(fixture_file, 'rb') objects = serializers.deserialize('json', fixture, ignorenonexistent=True) for obj in objects: obj.save() fixture.close() def unload_fixture(apps, schema_editor): "Brutally deleting all entries for this model..." MyModel = apps.get_model("yourapp", "ModelName") MyModel.objects.all().delete() class Migration(migrations.Migration): dependencies = [ ('yourapp', '0001_initial'), ] operations = [ migrations.RunPython(load_fixture, reverse_code=unload_fixture), ]
2.2. A simpler solution for
load_fixture (per @juliocesar's suggestion):
from django.core.management import call_command fixture_dir = os.path.abspath(os.path.join(os.path.dirname(__file__), '../fixtures')) fixture_filename = 'initial_data.json' def load_fixture(apps, schema_editor): fixture_file = os.path.join(fixture_dir, fixture_filename) call_command('loaddata', fixture_file)
Useful if you want to use a custom directory.
2.3. Simplest: calling
app_label will load fixtures from the
fixtures dir automatically :
from django.core.management import call_command fixture = 'initial_data' def load_fixture(apps, schema_editor): call_command('loaddata', fixture, app_label='yourapp')
_If you don't specify
app_label, loaddata will try to load
fixture filename from all apps fixtures directories (which you probably don't want)._
- Run it
python manage.py migrate <yourapp>