Added equality methods to Choices objects, and overrode + for Choices

for easy concatenation with other Choices and choice-like iterables.
Also wrote tests for them, and extended the readme to reflect this

README.rst

@@ -99,6 +99,20 @@ the third is the human-readable version:
         # ...
         status = models.IntegerField(choices=STATUS, default=STATUS.draft)
 
+Choices can be concatenated with the ``+`` operator, both to other Choices
+instances and other iterable objects that could be converted into Choices:
+
+.. code-block:: python
+
+    from model_utils import Choices
+
+    GENERIC_CHOICES = Choices((0, 'draft', _('draft')), (1, 'published', _('published')))
+
+    class Article(models.Model):
+        STATUS = GENERIC_CHOICES + [(2, 'featured', _('featured))]
+        # ...
+        status = models.IntegerField(choices=STATUS, default=STATUS.draft)
+
 
 StatusField
 ===========

model_utils/choices.py

@@ -73,6 +73,28 @@ class Choices(object):
     def __getitem__(self, index):
         return self._choices[index]
 
+    def __add__(self, other):
+        if isinstance(other, self.__class__):
+            other = other._full
+        else:
+            other = list(other)
+        return Choices(*(self._full + other))
+
+    def __radd__(self, other):
+        if isinstance(other, self.__class__):
+            other = other._full
+        else:
+            other = list(other)
+        return Choices(*(other + self._full))
+
+    def __eq__(self, other):
+        if isinstance(other, self.__class__):
+            return self._full == other._full
+        return False
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
     def __repr__(self):
         return '%s(%s)' % (self.__class__.__name__,
                           ', '.join(("%s" % repr(i) for i in self._full)))

model_utils/tests/tests.py

@@ -220,6 +220,15 @@ class ChoicesTests(TestCase):
         self.assertRaises(ValueError, Choices, ('a',))
 
 
+    def test_equality(self):
+        self.assertEqual(self.STATUS, Choices('DRAFT', 'PUBLISHED'))
+
+
+    def test_composability(self):
+        self.assertEqual(Choices('DRAFT') + Choices('PUBLISHED'), self.STATUS)
+        self.assertEqual(Choices('DRAFT') + ('PUBLISHED',), self.STATUS)
+        self.assertEqual(('DRAFT',) + Choices('PUBLISHED'), self.STATUS)
+
 
 class LabelChoicesTests(ChoicesTests):
     def setUp(self):
@@ -254,6 +263,14 @@ class LabelChoicesTests(ChoicesTests):
         self.assertEqual(len(self.STATUS), 3)
 
 
+    def test_equality(self):
+        self.assertEqual(self.STATUS, Choices(
+            ('DRAFT', 'is draft'),
+            ('PUBLISHED', 'is published'),
+            'DELETED',
+        ))
+
+
     def test_repr(self):
         self.assertEqual(repr(self.STATUS), "Choices" + repr((
             ('DRAFT', 'DRAFT', 'is draft'),
@@ -262,6 +279,22 @@ class LabelChoicesTests(ChoicesTests):
         )))
 
 
+    def test_composability(self):
+        self.assertEqual(
+            Choices(('DRAFT', 'is draft',)) + Choices(('PUBLISHED', 'is published'), 'DELETED'),
+            self.STATUS
+        )
+
+        self.assertEqual(
+            (('DRAFT', 'is draft',),) + Choices(('PUBLISHED', 'is published'), 'DELETED'),
+            self.STATUS
+        )
+
+        self.assertEqual(
+            Choices(('DRAFT', 'is draft',)) + (('PUBLISHED', 'is published'), 'DELETED'),
+            self.STATUS
+        )
+
 
 class IdentifierChoicesTests(ChoicesTests):
     def setUp(self):
@@ -298,6 +331,46 @@ class IdentifierChoicesTests(ChoicesTests):
         )))
 
 
+    def test_equality(self):
+        self.assertEqual(self.STATUS, Choices(
+            (0, 'DRAFT', 'is draft'),
+            (1, 'PUBLISHED', 'is published'),
+            (2, 'DELETED', 'is deleted'))
+        )
+
+
+    def test_composability(self):
+        self.assertEqual(
+            Choices(
+                (0, 'DRAFT', 'is draft'),
+                (1, 'PUBLISHED', 'is published')
+            ) + Choices(
+                (2, 'DELETED', 'is deleted'),
+            ),
+            self.STATUS
+        )
+
+        self.assertEqual(
+            Choices(
+                (0, 'DRAFT', 'is draft'),
+                (1, 'PUBLISHED', 'is published')
+            ) + (
+                (2, 'DELETED', 'is deleted'),
+            ),
+            self.STATUS
+        )
+
+        self.assertEqual(
+            (
+                (0, 'DRAFT', 'is draft'),
+                (1, 'PUBLISHED', 'is published')
+            ) + Choices(
+                (2, 'DELETED', 'is deleted'),
+            ),
+            self.STATUS
+        )
+
+
 class InheritanceManagerTests(TestCase):
     def setUp(self):
         self.child1 = InheritanceManagerTestChild1.objects.create()