Django: Checking CharField format in form with a regular expression

Question

class CapaForm(forms.Form):
    capa = forms.CharField(required=False)

Upon form submission I want to check the format of the capa field. I want to require the user to enter the capa format correctly as 6 numbers, a dash, and two numbers. (######-##)

def search(self):
    capa = self.cleaned_data.get('capa', None)

    if ("\d{6}\-\d{2}" or None) not in capa:
            raise forms.ValidationError("CAPA format needs to be ######-##!")

It's currently not letting me submit a correctly formatted capa and throws the ValidationError. I think the problem is I'm trying to compare a regular expression to an object. How can I check the format of the 'capa' the user tries to submit?

*********UPDATE

Everything is working now EXCEPT when I type the wrong format in the CAPA field. I get the error The view incidents.views.index didn't return an HttpResponse object. It returned None instead. Is this related to the changes I made?

from django.core.validators import RegexValidator
my_validator = RegexValidator("\d{6}\-\d{2}", "CAPA format needs to be ######-##.")

class CapaForm(forms.Form):
    capa = forms.CharField(
        label="CAPA",
        required=False, # Note: validators are not run against empty fields
        validators=[my_validator]
        )

def search(self):
    capa = self.cleaned_data.get('capa', None)
    query = Incident.objects.all()
    if capa is not '':
            query = query.filter(capa=capa)
    return(query)

Answer 1

First you need a regex validator: Django validators / regex validator

Then, add it into the validator list of your field: using validators in forms

Simple example below:

from django.core.validators import RegexValidator
my_validator = RegexValidator(r"A", "Your string should contain letter A in it.")

class MyForm(forms.Form):

    subject = forms.CharField(
        label="Test field",
        required=True,  # Note: validators are not run against empty fields
        validators=[my_validator]
    )