In the admin interface and newforms there is the brilliant helper of being able to define choices. You can use code like this:

APPROVAL_CHOICES = (('yes', 'Yes'),('no', 'No'),('cancelled', 'Cancelled'),
)client_approved = models.CharField(choices=APPROVAL_CHOICES)

to create a drop down box in your form and force the user to choose one of those options.

I'm just wondering if there is a way to define a set of choices where multiple can be chosen using checkboxes? (Would also be nice to be able to say that the user can select a maximum number of them.) It seems like it's a feature that is probably implemented, it's just I can't seem to find it in the documentation.

In terms of the forms library, you would use the MultipleChoiceField field with a CheckboxSelectMultiple widget to do that. You could validate the number of choices which were made by writing a validation method for the field:

class MyForm(forms.Form):my_field = forms.MultipleChoiceField(choices=SOME_CHOICES, widget=forms.CheckboxSelectMultiple())def clean_my_field(self):if len(self.cleaned_data['my_field']) > 3:raise forms.ValidationError('Select no more than 3.')return self.cleaned_data['my_field']

To get this in the admin application, you'd need to customise a ModelForm and override the form used in the appropriate ModelAdmin.