Prefilled admin inlines

class ProductRegexpFormset(BaseInlineFormSet):
    """
    Prefilled formset
    """

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        data = {item.shop_id: item.shop for item in self.queryset}
        self.shops = Shop.objects.exclude(id__in=data.keys())
        values = list(data.values())
        values.extend(self.shops)
        self.initial = [{'shop': shop} for shop in values]


class ProductRegexpInline(admin.StackedInline):
    """
    Prefilled inilines with disabled dropdown
    """
    formset = ProductRegexpFormset
    model = ProductRegexp
    fields = ('shop', ('name_regexp_list', 'info'))

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.shop_count = Shop.objects.count()

    def get_min_num(self, request, obj=None, **kwargs):
        return self.shop_count

    def get_max_num(self, request, obj=None, **kwargs):
        return self.shop_count

    def get_extra(self, request, obj=None, **kwargs):
        return self.shop_count

    def formfield_for_dbfield(self, db_field, **kwargs):
        if db_field.name == 'shop':
            field = db_field.formfield()
            field.widget.attrs['style'] = 'pointer-events: none;'
            return field
        return super().formfield_for_dbfield(db_field, **kwargs)