Django Dynamic Form Choices

dynamic_form.py

class CreateItemForm(forms.Form):
    categories = forms.MultipleChoiceField(
        # Must fill in choices and initial from the DB at runtime
        widget=forms.CheckboxSelectMultiple(),
        required=False,
        )

    def __init__(self, *args, **kwargs):
        user = kwargs['user']
        del kwargs['user']

        super(CreateItemForm, self).__init__(*args, **kwargs)

        # Get all the possible categories, you could use info from *args, **kwargs 
        # here to filter the list of categories if you wanted.  (i.e. to ones that 
        # are available to this user, etc.) 
        all_categories = Category.objects.order_by('name')

        self.fields['categories'].choices = (
            [(c.id, c.name) for c in all_categories])