Django 2.1 admin.py changeform_view method error with blank tables

Question

In my admin.py i use changeform_view method for mantain some data into an add form after save Fo example one of my admin class is:

class temp_mainAdmin(admin.ModelAdmin):

    form = TempMainForm

    list_filter = ('t_type',)
    list_display = ('descr', 't_type', 'notes', 'dt', 'active')

    def save_model(self, request, obj, form, change):
        obj.user = request.user
        super(temp_mainAdmin, self).save_model(request, obj, form, change)

    def changeform_view(self, request, obj_id, form_url, extra_context=None):

        try:            
            l_mod = temp_main.objects.latest('id')

            extra_context = {
                'lmod': l_mod,
                'oId': obj_id
            }

            return super(temp_mainAdmin, self).changeform_view(request, obj_id,form_url, extra_context=extra_context)
    except Exception:
        pass


admin.site.register(temp_main, temp_mainAdmin, )

The point is that if the temp_main table has at least one record all was done, but if instead the table is blank, when i try to open "add" form i receive the error

DoesNotExist at /admin/backend/temp_main/add/ temp_add matching query does not exist.

if i remove the entire changeform_view method from my class all was done except for the fact that after press "Save and add another" i don't have my fields already populated.

Was wrong in my changeform_view method?

p.s.: i use PostgreeSQL as backend db

So many thanks in advance

Answer 1

You could check for query in this fashion inside method:

try:
    l_mod = temp_main.objects.latest('id')
except Exception:
    l_mod = None