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2018-01-21 Django

Django Adding Default Data After Migrations

Django Adding default data After Migrations#

We are talking RunPython here not fixtures. Django Fixures are used to created initial data for models - however they are not automatically run as part of migrations.

Create an empty migration (remember to have already created the migrations for the table you are adding default data for)

./manage.py makemigrations <app_name> --empty -n <name_of_migration>

It will probably already have a dependency of the previous migration

Acquire the model with:

ModelName = apps.get_model("<app_name>", "<model_name>")

Then do actions on it much like in the docs:

    from django.db import migrations

    def forwards_func(apps, schema_editor):
        # We get the model from the versioned app registry;
        # if we directly import it, it'll be the wrong version
        Country = apps.get_model("myapp", "Country")
        db_alias = schema_editor.connection.alias
        Country.objects.using(db_alias).bulk_create([
            Country(name="USA", code="us"),
            Country(name="France", code="fr"),
        ])

    def reverse_func(apps, schema_editor):
        # forwards_func() creates two Country instances,
        # so reverse_func() should delete them.
        Country = apps.get_model("myapp", "Country")
        db_alias = schema_editor.connection.alias
        Country.objects.using(db_alias).filter(name="USA", code="us").delete()
        Country.objects.using(db_alias).filter(name="France", code="fr").delete()

    class Migration(migrations.Migration):

        dependencies = []

        operations = [
            migrations.RunPython(forwards_func, reverse_func),
        ]

Sources#