Generate Django Model Choices Dynamically

I recently used Django admin to add and remove data through the backend UI. The model field used choices to render a dropdown, but later I found that every time the choices list changed, Django wanted to generate a new migration file. To avoid that, I looked for a way to make the choices dynamic.

Suppose we start with a model like this:

from django.db import models


class Dynamics(models.Model):
    source = models.CharField(max_length=64, choices=(
        ('baidu', 'baidu'),
        ('google', 'google'),
    ))

After running makemigrations, the generated migration contains the choices inline:

operations = [
    migrations.CreateModel(
        name='Dynamics',
        fields=[
            ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
            ('source', models.CharField(choices=[('baidu', 'baidu'), ('google', 'google')], max_length=64)),
        ],
    ),
]

That means every later change to choices triggers a new migration.

One workaround is to generate the choices from a helper function:

from django.db import models


def get_source_choices():
    return (
        ('baidu', 'baidu'),
        ('google', 'google'),
        ('duckduckgo', 'duckduckgo'),
    )


class Dynamics(models.Model):
    source = models.CharField(max_length=64, choices=get_source_choices())

Then modify the migration file that was generated earlier so that it imports and calls the same function:

from django.db import migrations, models
from ..models import get_source_choices


class Migration(migrations.Migration):

    initial = True

    dependencies = [
    ]

    operations = [
        migrations.CreateModel(
            name='Dynamics',
            fields=[
                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('source', models.CharField(choices=get_source_choices(), max_length=64)),
            ],
        ),
    ]

After that, future changes only need to update get_source_choices(), and no new migration will be generated just because the dropdown options changed.