haplo · May 14, 2012 18:52 · May 14, 2012 · May 14, 2012
diff --git a/admin.py b/admin.py
@@ -10,6 +10,9 @@ class ConcreteBlankFilter(BlankFilter):
             title = "some title"
             parameter_name = "model_field_name"
 
+    This has been inspired (read "almost an exact copy of") this solution
+    at StackOverflow: http://stackoverflow.com/a/9593302/519510
+
     """
     title = ''
     parameter_name = ''

diff --git a/admin.py b/admin.py
@@ -0,0 +1,41 @@
+from django.contrib import admin
+
+
+class BlankFilter(admin.SimpleListFilter):
+    """Abstract base class for filtering blank fields.
+
+    To use define a subclass that defines title and parameter_name fields:
+
+        class ConcreteBlankFilter(BlankFilter):
+            title = "some title"
+            parameter_name = "model_field_name"
+
+    """
+    title = ''
+    parameter_name = ''
+
+    def lookups(self, request, model_admin):
+        return (
+            ('1', _('Has value'), ),
+            ('0', _('Empty value'), ),
+        )
+
+    def queryset(self, request, queryset):
+        kwargs = {
+            unicode(self.parameter_name): '',
+        }
+        if self.value() == '0':
+            return queryset.filter(**kwargs)
+        if self.value() == '1':
+            return queryset.exclude(**kwargs)
+        return queryset
+
+
+class ConcreteBlankFilter(BlankFilter):
+    title = "this filter is usable in "
+    parameter_name = "model_field_name" # model_field_name should correspond to 
+                                        # a field with blank=True
+
+
+class SomeModelAdmin(admin.ModelAdmin):
+    list_filter = [ConcreteBlankFilter]