Fixed indexing into Choices so its useful.

CHANGES.rst

@@ -4,6 +4,10 @@ CHANGES
 master (unreleased)
 -------------------
 
+* Indexing into a ``Choices`` instance now translates database representations
+  to human-readable choice names, rather than simply indexing into an array of
+  choice tuples. (Indexing into ``Choices`` was previously not documented.)
+
 * Fix bug in `InheritanceManager` with grandchild classes on Django 1.6+;
   `select_subclasses('child', 'child__grandchild')` would only ever get to the
   child class. Thanks Keryn Knight for report and proposed fix.

docs/utilities.rst

@@ -52,6 +52,13 @@ the third is the human-readable version:
         STATUS = Choices((0, 'draft', _('draft')), (1, 'published', _('published')))
         status = models.IntegerField(choices=STATUS, default=STATUS.draft)
 
+You can index into a ``Choices`` instance to translate a database
+representation to its display name:
+
+.. code-block:: python
+
+    status_display = Article.STATUS[article.status]
+
 Option groups can also be used with ``Choices``; in that case each
 argument is a tuple consisting of the option group name and a list of
 options, where each option in the list is either a string, a two-tuple,

model_utils/choices.py

@@ -46,8 +46,10 @@ class Choices(object):
         self._triples = []
         # list of choices as (db, human-readable) - can include optgroups
         self._doubles = []
+        # dictionary mapping db representation to human-readable
+        self._display_map = {}
         # dictionary mapping Python identifier to db representation
-        self._mapping = {}
+        self._identifier_map = {}
         # set of db representations
         self._db_values = set()
 
@@ -55,7 +57,8 @@ class Choices(object):
 
 
     def _store(self, triple, triple_collector, double_collector):
-        self._mapping[triple[1]] = triple[0]
+        self._identifier_map[triple[1]] = triple[0]
+        self._display_map[triple[0]] = triple[2]
         self._db_values.add(triple[0])
         triple_collector.append(triple)
         double_collector.append((triple[0], triple[2]))
@@ -104,13 +107,13 @@ class Choices(object):
 
     def __getattr__(self, attname):
         try:
-            return self._mapping[attname]
+            return self._identifier_map[attname]
         except KeyError:
             raise AttributeError(attname)
 
 
-    def __getitem__(self, index):
-        return self._doubles[index]
+    def __getitem__(self, key):
+        return self._display_map[key]
 
 
     def __add__(self, other):

model_utils/tests/tests.py

@@ -200,7 +200,7 @@ class ChoicesTests(TestCase):
 
 
     def test_indexing(self):
-        self.assertEqual(self.STATUS[1], ('PUBLISHED', 'PUBLISHED'))
+        self.assertEqual(self.STATUS['PUBLISHED'], 'PUBLISHED')
 
 
     def test_iteration(self):
@@ -276,7 +276,7 @@ class LabelChoicesTests(ChoicesTests):
 
 
     def test_indexing(self):
-        self.assertEqual(self.STATUS[1], ('PUBLISHED', 'is published'))
+        self.assertEqual(self.STATUS['PUBLISHED'], 'is published')
 
 
     def test_default(self):
@@ -380,7 +380,7 @@ class IdentifierChoicesTests(ChoicesTests):
 
 
     def test_indexing(self):
-        self.assertEqual(self.STATUS[1], (1, 'is published'))
+        self.assertEqual(self.STATUS[1], 'is published')
 
 
     def test_getattr(self):