Add non-null and unique field with already populated model

Question

I have one model in my app running in a server with a few entries. I need to add a SlugField, unique and not-null for this model. The SlugField will be

Answer 1

You do your model changes (add field, change, etc), then you call manage.py makemigrations, then apply the migrations with manage.py migrate

You can add the field with null=True, then you e.g. make a script to populate it one time

Otherwise, if you need to populate the field within the migration you can write a custom one, see https://docs.djangoproject.com/en/1.7/ref/migration-operations/#writing-your-own