class SignUpForm(forms.ModelForm):
    confirm_password = forms.CharField(max_length=50)

class Meta:
    model = User
    fields = ['password', 'email', 'first_name', 'last_name']

def is_valid(self):
    if super(SignUpForm, self).is_valid() and self.confirm_password == self.instance.password:
        return True
    else:
        False

def save(self, commit=True):
    if self.is_valid():
        self.instance.objects.create_user(username=self.instance.email, email=self.instance.email,
                                          password=self.instance.password, first_name=self.first_name,
                                          last_name=self.last_name).save()