Question: We can make the django filter with "`in`" expression sending comma separated string. Such as

```
import django_filters

class NumberInFilter(django_filters.BaseInFilter, django_filters.NumberFilter):
    pass

class BookFilter(django_filters.FilterSet):
    author = NumberInFilter(field_name="author__id", lookup_expr="in")

```

However, I was looking for way to send comma separated query-data and get response which do not have the query-data. something like

```
class BookFilter(django_filters.FilterSet):
    author = NumberInFilter(field_name="author__id", lookup_expr="not_in")

```

Definitely there is nothing like "`not_in`". Can you please give me a solution to achieve this?

Answer: 
Seems there is a more optimal solution. You can use the NumberFilters' `exclude=True` option like this:

```
class BookFilter(django_filters.FilterSet):
    author = NumberInFilter(
        field_name="author__id", 
        lookup_expr="in", 
        exclude=True
    )

```
Just wanted to add what I finally got,

```
class BookFilter(django_filters.FilterSet):
    author = django_filters.NumberFilter(method='filter_author')

    def filter_author(self, queryset, name, value):
        if value:
            return queryset.exclude(author__id__in=value.split(','))
        return queryset

```