ModelChoiceField shows objects instead on contents

Question

How can I change my code to show contents instead of objects ?

forms.py:

unit_set = AnalysisVariableUnit.objects.all()
for unit in AnalysisVariableUnit.objects.all():
    print(unit.__dict__)

class AnalyysimuuttujaForm(forms.Form):
    technical_name = forms.CharField(required=False,
                                     widget=forms.TextInput(
                                        attrs={
                                            'class':'readonly_able tn'
                                            }
                                        ))
    decimals = forms.ChoiceField(choices=CHOICES_DS)
    decimals_format = forms.ChoiceField(choices=CHOICES_DS)
    units = forms.ModelChoiceField(
            required=False,
            widget=forms.Select,
            queryset=unit_set,
        )   

this outputs:

{'_state': <django.db.models.base.ModelState object at 0x7f2038ea51d0>, 'id': 1, 'contents': 'indeksipisteluku'}
{'_state': <django.db.models.base.ModelState object at 0x7f2038ea5240>, 'id': 2, 'contents': '%'}

I want to have 'indeksipisteluku' and '%' as selectables in my drop down, which now shows:

Answer 1

AnalysisVariableUnit object (...) is the default output of Django's __str__ for a model.

Add a descriptive __str__ to your model:

def __str__(self):
    return str(self.contents)