I’ve encountered situations using Django’s ModelForm where I’ve needed the form to validate differently then the default behavior in various instances. Here’s an example of how I changed all the fields from the default of not being required to all being required without much effort:

class AddressRequiredForm(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        super(AddressForm, self).__init__(*args, **kwargs)
        for name, field in self.fields.iteritems():
            if name not in ['address2',]:
                field.required = True

    class Meta:
        model = Address

This is pretty simple, but it saved me a lot of time by not having to re-type each field name with a new set of properties.