How to group the choices in a Django Select widget?

Question

Is it possible to created named choice groups in a Django select (dropdown) widget, when that widget is on a form that is auto-generated from a data Model?

Answer 1

Here's what worked for me, not extending any of the current django classes:

I have a list of types of organism, given the different Kingdoms as the optgroup. In a form OrganismForm, you can select the organism from a drop-down select box, and they are ordered by the optgroup of the Kingdom, and then all of the organisms from that kingdom. Like so:

  [----------------|V]
  |Plantae         |
  |  Angiosperm    |
  |  Conifer       |
  |Animalia        |
  |  Mammal        |
  |  Amphibian     |
  |  Marsupial     |
  |Fungi           |
  |  Zygomycota    |
  |  Ascomycota    |
  |  Basidiomycota |
  |  Deuteromycota |
  |...             |
  |________________|

models.py

from django.models import Model

class Kingdom(Model):
    name = models.CharField(max_length=16)

class Organism(Model):
    kingdom = models.ForeignKeyField(Kingdom)
    name = models.CharField(max_length=64)

forms.py:

from models import Kingdom, Organism

class OrganismForm(forms.ModelForm):
    organism = forms.ModelChoiceField(
        queryset=Organism.objects.all().order_by('kingdom__name', 'name')
    )
    class Meta:
        model = Organism

views.py:

from models import Organism, Kingdom
from forms import OrganismForm
form = OrganismForm()
form.fields['organism'].choices = list()

# Now loop the kingdoms, to get all organisms in each.
for k in Kingdom.objects.all():
    # Append the tuple of OptGroup Name, Organism.
    form.fields['organism'].choices = form.fields['organism'].choices.append(
        (
            k.name, # First tuple part is the optgroup name/label
            list( # Second tuple part is a list of tuples for each option.
                (o.id, o.name) for o in Organism.objects.filter(kingdom=k).order_by('name')
                # Each option itself is a tuple of id and name for the label.
            )
        )
    )