How do you dynamically hide form fields in Django?

Question

I am making a profile form in Django. There are a lot of optional extra profile fields but I would only like to show two at a time. How do I hide or remove the fields I do not want to show dynamically?

Here is what I have so far:

class UserProfileForm(forms.ModelForm):
    extra_fields = ('field1', 'field2', 'field3')
    extra_field_total = 2

    class Meta:
        model = UserProfile

    def __init__(self, *args, **kwargs):
        extra_field_count = 0
        for key, field in self.base_fields.iteritems():
            if key in self.extra_fields:
                if extra_field_count < self.extra_field_total:
                    extra_field_count += 1
                else:
                    # do something here to hide or remove field
        super(UserProfileForm, self).__init__(*args, **kwargs)

Answer 1

I think I found my answer.

First I tried:

field.widget = field.hidden_widget

which didn't work.

The correct way happens to be:

field.widget = field.hidden_widget()

Answer 2

Can also use

def __init__(self, instance, *args, **kwargs):    
    super(FormClass, self).__init__(instance=instance, *args, **kwargs)
    if instance and instance.item:
        del self.fields['field_for_item']