Modify value of a Django form field during clean() and validate again

Question

I want to do something like this:

class UsuarioForm(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        super(UsuarioForm, self).__init__(*args, **kwargs)
        self.fields['cpf'].widget.attrs['maxlength'] = 14
        self.fields['telefone'].widget.attrs['maxlength'] = 15
        self.fields['celular'].widget.attrs['maxlength'] = 15



    nome = forms.CharField(widget=forms.TextInput(attrs={'readonly': True,
                                                         'icone': 'fa fa-font'}))

    usuario = forms.CharField(widget=forms.TextInput(attrs={'readonly': True,
                                                         'icone': 'fa fa-user'}))



    def clean(self):

        cleaned_data = self.cleaned_data

        self.data['cpf'] = re.sub("[\.-]", "", self.data['cpf'])

        clean_data_again_to_revalidate_the_field


    class Meta:
        model = Usuario

        exclude = ['codigo', 'estabelecimento', 'dono', 'data', 'estabelecimento', 'cargo', 'usuario']


        widgets = {

            'cpf': forms.TextInput(attrs={'placeholder': Text().cpf(),
                                          'icone': 'fa fa-credit-card',
                                          'id':'cpf',

                                          }),

            'telefone': forms.TextInput(attrs={'placeholder': Text().telefone(),
                                               'icone': 'fa fa-phone'.decode('utf-8'),
                                               'id': Text().telefone()}),

            'celular': forms.TextInput(attrs={'placeholder': Text().celular(),
                                              'icone': 'fa fa-mobile',
                                              'id': Text().celular()}),
        }

I want to change the field CPF to remove dots. After, I want to validate the field again. Is it possible?

Also, the self.data['cpf'] receiving the value is not possible. it is failing with: This QueryDict instance is immutable.

I created the method clean_cpf, but it is never called. I think because the cpf field do not appear in cleaned_data, since is invalid in the format I receive the data.

Also, the cpf is not in the cleaned_data. I think because is invalid. The cpf has the max length of 11, but when it come from the screen, the field has 14 characters. This is why I need to change the field and validate it again.

If the QueryDict instance is immutable.. before reassigning it with a different value try `self.data._mutable = True` and then `self.data['cpf'] = re.sub("[\.-]", "", self.data['cpf'])` although this should be less preferred. — Arpit Goyal, Oct 20 '17 at 03:12
@ArpitGoyal `QueryDict._mutable` is a protected attribute, you should not touch it (unless you really know what you're doing _and_ have no other sensible solution). In this case there is a _documented_ correct way to get a mutable QueryDict : "To get a mutable version you need to use QueryDict.copy()" — bruno desthuilliers, Oct 20 '17 at 07:29
@DiegoMartins : if the linked questions doesn't solve your problem please post a comment explaining why - maybe you need a custom FormField, or maybe you should better accept a dotted value matching a regexp... — bruno desthuilliers, Oct 20 '17 at 07:33
@bruno desthuilliers I explained. The link suggest to use a clean_cpf method. But his method is never called, because the cpf is not valid. I think the method is not called because of this from the docs: If, at any time, any of the methods raise ValidationError, the validation stops and that error is raised [link](https://docs.djangoproject.com/en/1.11/ref/forms/validation/) — Diego Martins, Oct 20 '17 at 10:30
@DiegoMartins good point, should have read more in depth, sorry. — bruno desthuilliers, Oct 20 '17 at 10:47

score 3 · Accepted Answer · answered Oct 20 '17 at 11:05

A q&d hack would be to fix the value in data directly in the form's __init__ (nb : untested code):

class UsuarioForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(UsuarioForm, self).__init__(*args, **kwargs)
        if self.data:
            # make the QueryDict mutable
            self.data = self.data.copy()
            # remove dots from data["cpf"]
            if "cpf" in self.data:
                self.data["cpf"] = self.data["cpf"].replace(".", "")
        # ...

But if you still get validation errors, when redisplaying the form the "cpf" field's data will be renderer without the dots.

A cleaner solution would be to use a custom "CreditCard" field instead since your cpf field seems to expected a credit card number. There are a couple third part implementations on the web, that might be used out of the box or at least provide a starting point.

As a side note: you override the default widgets in your form's Meta, then override the same field's "max_length" in the form's __init__, which is not quite DRY. You should set the maxlength directly in the Meta.widgets part.

Many thanks.It worked, I was able to modify the CPF before the validation and the Model Form is working. Thanks a lot. — Diego Martins, Oct 20 '17 at 23:50

Modify value of a Django form field during clean() and validate again

1 Answers1