Django admin: make field editable in add but not edit

Question

I\'ve got a model similar to this:

class Product(models.Model):
    third_party_id = models.CharField(max_length=64, blank=False, unique=True)

Answer 1

I am not sure if this is the best way, but you could define your own form for the admin. And custom validate your third_party_id, rejecting if it is already set:

Admin.py

class ProductAdminForm(forms.ModelForm):
    class Meta:
        model = Product

    def clean_third_party_id(self):
        cleaned_data = self.cleaned_data
        third_party_id = cleaned_data['third_party_id']
        id = cleaned_data['id']
        obj = Product.objects.get(id=id)
        if obj.third_party_id != third_party_id:
            raise ValidationError("You cannot edit third_party_id, it must stay as %s" % obj.third_party_id)
         return third_party_id


class ProductAdmin(admin.Admin):
    form = [ProductAdminForm,]