python - How to Check for Unique Data in Django Form? -

i'm following examples posted on django formset documents regarding custom formset validation slight modification. found flaw in example unsure how fix it. there way check uniqueness in data if 1 of 3 input field not filled out? apparently, empty form recorded "none" forces me @ least fill out 2/3 sets of input field (firstname/lastname); otherwise, register duplicates. illustrate mean:

forms.py

class userinfo (forms.form):      first_name = forms.charfield (max_length = 20, required = false)     last_name = forms.charfield (max_length = 20, required = false)   class baseuserinfoformset (baseformset):      def clean (self):         if (self.errors):             return          firstnames = []         lastnames = []         errors = []          form in self.forms:             firstname = form.cleaned_data.get ('first_name')             lastname = form.cleaned_data.get ('last_name')              if ((firstname in firstnames) or (lastname in lastnames)) , len (errors) < 2:                 errors.append ('first and/or last name must unique')             if ((firstname == '') or (lastname == '')) , len (errors) < 2:                 errors.append ('first and/or last name cannot blanked')              firstnames.append (firstname)             lastnames.append (lastname)             print ('first name list: ', firstnames)             print ('last name list: ', lastnames)          if errors:             raise forms.validationerror (errors)          return self.cleaned_data 

with 1 set of firstname/lastname filled out, here's result console.

first name list:  ['john'] last name list:  ['doe']  first name list:  ['john', none] last name list:  ['doe', none]  first name list:  ['john', none, none] last name list:  ['doe', none, none] 

because there duplicate "none", triggered error:

errors.append ('first and/or last name must unique') 

just clarify, not need blank values, why not make fields required. remove none issue altogether, fields required.

else, add values list if not empty

if firstname:      firstnames.append(firstname) if lastname:      lastnames.append(lastname)