Django 2.0 Populating Database with a Script

Question

I'm trying to populate my Django database with a script so I don't have to enter in the data manually. So far I have the following:

from my_app.models import ModelInApp
import django

django.setup()


def add_data(data1, data2):
    d, created = ModelInApp.objects.get_or_create(data1=data1, data2=data2)
    print("- Data: {0}, Created: {1}".format(str(d), str(created)))
    return d


def populate():
    # data is a list of lists
    for row in data:
        data1 = row[0]
        data2 = row[1]
        add_data(data1, data2)


if __name__ == "__main__":
    populate()

The data variable is a list of lists containing the data I want to put into my database. The problem is, when I run the script, I get a django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet. error. I am using PostgreSQL as the database.

What am I doing wrong?

Answer 1

I know it's been like forever but.. Although not technically a script, Django allows database seeding by creating a fixture

The documentation is very much intuitive. This is always my go-to method when pre-populating a database in Django. For example, if you have a model Cars:

class Cars(models.Model):
    make = models.CharField(max_length=50)
    color = models.CharField(max_length=50)

You can create a seeding fixture cars.json like:

[
  {
    "model":"myapp.cars",
    "pk":1,
    "fields":{
      "make": "Audi",
      "color":"Black"
    }
  },
  {
    "model":"myapp.cars",
    "pk":2,
    "fields":{
      "make": "Aston Martin",
      "color":"Blue"
    }
  }
]

To prepopulate the DB, just run ./manage.py loaddata cars.json

I find this is the best option if you for example have to load data like all car models or all countries and their flags or sth in the same lines for every web app you create...

Answer 2

The fast way to work it out is to populate your DB from Django shell (python manage.py shell). Your code without import django and django.setup() should work fine. Fast & dirty ;)

In case you need to add data from time to time, consider writing a management command. This will allow you to call python manage.py my_command_name datafile.dat. You can implement whatever logic inside the command (data from file or API, create or update).

Another way to add data is to use data migration: https://simpleisbetterthancomplex.com/tutorial/2017/09/26/how-to-create-django-data-migrations.html

Also, consider using bulk_create to make things more efficient (filter the data list before to avoid duplicates)