python - Django: form save exculde certain field -

i not understand official document exclude .

set exclude attribute of modelform‘s inner meta class list of fields excluded form.  example:  class partialauthorform(modelform):     class meta:         model = author         exclude = ['title'] since author model has 3 fields name, title , birth_date, result in fields name , birth_date being present on form. 

understanding follows: django form save method save form data.if 1 set exclude =('something',) , 'something' field not show on frontend , wouldn't save while calling form save method.
when document saying, 'something' field still show.what's matter?

want add fields form validating can show on frontend without saving.it stange find nothing need.

**update** 

my code :

class profileform(html5mixin, forms.modelform):      password1 = forms.charfield(label=_("password"),                                 widget=forms.passwordinput(render_value=false))     password2 = forms.charfield(label=_("password (again)"),                                 widget=forms.passwordinput(render_value=false))      captcha_text = forms.charfield(label=_("captcha"),                                 widget=forms.textinput())     captcha_detext = forms.charfield(                                 widget=forms.hiddeninput())      class meta:         model = user         fields = ("email", "username")         exclude = ['captcha_text']      def __init__(self, *args, **kwargs):         super(profileform, self).__init__(*args, **kwargs)         ..........      def clean_username(self):         .....      def clean_password2(self):         ....      def save(self, *args, **kwargs):         """         create new user. if no username supplied (may hidden         via ``accounts_profile_form_exclude_fields`` or         ``accounts_no_username``), generate unique username,         if profile pages enabled, still have         use profile's slug.         """         ..............      def get_profile_fields_form(self):         return profilefieldsform 

if exclude affect model defined under class meta , exclude = ['captcha_text'] not work?

exclude = ['title'] exclude field form, not model. form.save() try save model instance available fields, model might throw error pertaining missing field.

to add fields in model form, this:

class partialauthorform (modelform):     extra_field = forms.integerfield()      class meta:         model = author      def save(self, *args, **kwargs):         # self.cleaned_data['extra_field']         super(partialauthorform, self).save(*args, **kwargs) 

but make sure there no field called "partialauthorform" in model author.