[Django]-Filter by no field in Django Admin

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ModelAdmin list_filter accepts either fields or a class inheriting from django.contrib.admin.SimpleListFilter, which you need to provide the title and parameter_name attributes to and override the lookups and queryset methods. In this case you could take the second option and do something like:

class ItemCountListFilter(admin.SimpleListFilter):
    # Human-readable title which will be displayed in the
    # right admin sidebar just above the filter options.
    title = 'item count'

    # Parameter for the filter that will be used in the URL query.
    parameter_name = 'count'

    def lookups(self, request, model_admin):
        """
        Returns a list of tuples. The first element in each
        tuple is the coded value for the option that will
        appear in the URL query. The second element is the
        human-readable name for the option that will appear
        in the right sidebar.
        """
        max_value = Sale.objects.all().annotate(
            count_items=Count('sales_det')
        ).aggregate(max_value=Max('count_items'))['max_value']
        return [(i, i) for i in range(0, max_value)]

    def queryset(self, request, queryset):
        """
        Returns the filtered queryset based on the value
        provided in the query string and retrievable via
        `self.value()`.
        """
        # Compare the requested value (either '80s' or '90s')
        # to decide how to filter the queryset.
        return queryset.annotate(
            count_items=Count('sales_det')
        ).filter(
            count_items=self.value()
        )


class SaleAdmin(admin.ModelAdmin):
    list_display = ('__unicode__', 'customer', 'get_itens', 'get_total')
    readonly_fields = ['get_total']
    list_filter = ('customer', ItemCountListFilter)


admin.site.register(Sale, SaleAdmin)
👤suselrd

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