python - Practical Django Projects - Page 168 -

on page 168, there 2 pieces of code :

def clean_password2(self):    if self.cleaned_data['password1'] != self.cleaned_data['password2']:       raise forms.validationerror("you must type same password each time")    return self.cleaned_data['password2']  def clean(self):    if 'password1' in self.cleaned_data , 'password2' in self.cleaned_data:       if self.cleaned_data['password1'] != self.cleaned_data['password2']:          raise forms.validationerror("you must type same password each time")    return self.cleaned_data 

in second case, code checks whether 'password1' , 'password2' have value. in first case, there no such check. why ?

in clean_password2 validating password2 field exists on form , don't need check existence of in self.cleaned_data. doesn't mean couldn't check eixstence of password1, however.

the clean method validating whole form , has no guarantees of present.