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

<pre><code>APPROVAL_CHOICES = (
    ('yes', 'Yes'),
    ('no', 'No'),
    ('cancelled', 'Cancelled'),
)

client_approved = models.CharField(choices=APPROVAL_CHOICES)
</code></pre>

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

<p>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.</p>

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
.