Django Model Inheritance (DMI) Examples

Here lies the example models used in the Ins & Outs of Models Inheritance (slides) presented at DjangoCon 2019. In some cases, the names have been changed to protect the innocent models from redundancy.

Exploring the Models

1. Migrate to create tables:

python3 manage migrate

2. Run shell or shell_plus This project includes django-extensions so you use shell plus and print all the SQL executed with --print-sql.

python3 manage shell_plus --print-sql

Example with Multi-Table Inheritance

from mti.models import BigCat  # shell_plus auto imports
from mti.models import Cheetah
from mti.models import Lion

Lion.objects.create(name='Simba', giraffes_hunted=0)
Cheetah.objects.create(name='Chester')
cats = BigCat.objects.all()
cats[0].lion.name

3. The database is sqlite for convenience. To query the command line:

python3 manage dbshell

sqlite> .tables
abstract_giraffe            django_migrations
abstract_zebra              django_session
auth_group                  gfk_blog
auth_group_permissions      gfk_comment
auth_permission             mti_bigcat
auth_user                   mti_cheetah
auth_user_groups            mti_lion
auth_user_user_permissions  polymorph_artproject
basic_leg                   polymorph_project
basic_snowgiraffe           polymorph_researchproject
basic_tongue                proxy_person
django_admin_log            sti_vehicle
django_content_type         tmodels_typedanimal
sqlite> .schema basic_snowgiraffe
CREATE TABLE IF NOT EXISTS "basic_snowgiraffe" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "name" varchar(255) NOT NULL);