Backport r87613 to make OrderedDict subclassing match dict subclassing.

rhettinger · rhettinger · commit 1d879f685258 · 2011-01-04T20:57:19.000Z
diff --git a/Lib/collections.py b/Lib/collections.py
@@ -21,7 +21,7 @@
 class _Link(object):
     __slots__ = 'prev', 'next', 'key', '__weakref__'
 
-class OrderedDict(dict, MutableMapping):
+class OrderedDict(dict):
     'Dictionary that remembers insertion order'
     # An inherited dict maps keys to values.
     # The inherited dict provides __getitem__, __len__, __contains__, and get.
@@ -50,7 +50,7 @@ def __init__(self, *args, **kwds):
             self.__root = root = _Link()    # sentinel node for the doubly linked list
             root.prev = root.next = root
             self.__map = {}
-        self.update(*args, **kwds)
+        self.__update(*args, **kwds)
 
     def clear(self):
         'od.clear() -> None.  Remove all items from od.'
@@ -109,13 +109,29 @@ def __reduce__(self):
             return (self.__class__, (items,), inst_dict)
         return self.__class__, (items,)
 
-    setdefault = MutableMapping.setdefault
-    update = MutableMapping.update
-    pop = MutableMapping.pop
+    update = __update = MutableMapping.update
     keys = MutableMapping.keys
     values = MutableMapping.values
     items = MutableMapping.items
 
+    __marker = object()
+
+    def pop(self, key, default=__marker):
+        if key in self:
+            result = self[key]
+            del self[key]
+            return result
+        if default is self.__marker:
+            raise KeyError(key)
+        return default
+
+    def setdefault(self, key, default=None):
+        'od.setdefault(k[,d]) -> od.get(k,d), also set od[k]=d if k not in od'
+        if key in self:
+            return self[key]
+        self[key] = default
+        return default
+
     def popitem(self, last=True):
         '''od.popitem() -> (k, v), return and remove a (key, value) pair.
         Pairs are returned in LIFO order if last is true or FIFO order if false.
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
@@ -792,6 +792,10 @@ def test_update(self):
         self.assertEqual(list(d.items()),
             [('a', 1), ('b', 2), ('c', 3), ('d', 4), ('e', 5), ('f', 6), ('g', 7)])
 
+    def test_abc(self):
+        self.assertTrue(isinstance(OrderedDict(), MutableMapping))
+        self.assertTrue(issubclass(OrderedDict, MutableMapping))
+
     def test_clear(self):
         pairs = [('c', 1), ('b', 2), ('a', 3), ('d', 4), ('e', 5), ('f', 6)]
         shuffle(pairs)
@@ -850,6 +854,17 @@ def test_pop(self):
         self.assertEqual(len(od), 0)
         self.assertEqual(od.pop(k, 12345), 12345)
 
+        # make sure pop still works when __missing__ is defined
+        class Missing(OrderedDict):
+            def __missing__(self, key):
+                return 0
+        m = Missing(a=1)
+        self.assertEqual(m.pop('b', 5), 5)
+        self.assertEqual(m.pop('a', 6), 1)
+        self.assertEqual(m.pop('a', 6), 6)
+        with self.assertRaises(KeyError):
+            m.pop('a')
+
     def test_equality(self):
         pairs = [('c', 1), ('b', 2), ('a', 3), ('d', 4), ('e', 5), ('f', 6)]
         shuffle(pairs)
@@ -934,6 +949,12 @@ def test_setdefault(self):
         # make sure 'x' is added to the end
         self.assertEqual(list(od.items())[-1], ('x', 10))
 
+        # make sure setdefault still works when __missing__ is defined
+        class Missing(OrderedDict):
+            def __missing__(self, key):
+                return 0
+        self.assertEqual(Missing().setdefault(5, 9), 9)
+
     def test_reinsert(self):
         # Given insert a, insert b, delete a, re-insert a,
         # verify that a is now later than b.
@@ -945,6 +966,13 @@ def test_reinsert(self):
         self.assertEqual(list(od.items()), [('b', 2), ('a', 1)])
 
 
+    def test_override_update(self):
+        # Verify that subclasses can override update() without breaking __init__()
+        class MyOD(OrderedDict):
+            def update(self, *args, **kwds):
+                raise Exception()
+        items = [('a', 1), ('c', 3), ('b', 2)]
+        self.assertEqual(list(MyOD(items).items()), items)
 
 class GeneralMappingTests(mapping_tests.BasicTestMappingProtocol):
     type2test = OrderedDict
