{{form.username}}

self.fields["my_field"].widget.attrs.update({'class' : 'myfieldclass'})

class RegistrationForm(UserCreationForm):
	def __init__(self, *args, **kwargs):
		super(RegistrationForm, self).__init__(*args, **kwargs)
		for name, field in self.fields.items():
				  field.widget.attrs.update({'class':'form-control input-lg panjo-input-validation-target'})