Support all the new stuff supported by the new pickle code:

- subclasses of list or dict
- __reduce__ returning a 4-tuple or 5-tuple
- slots

Lib/copy.py

@@ -7,7 +7,7 @@ Interface summary:
         x = copy.copy(y)        # make a shallow copy of y
         x = copy.deepcopy(y)    # make a deep copy of y
 
-For module specific errors, copy.error is raised.
+For module specific errors, copy.Error is raised.
 
 The difference between shallow and deep copying is only relevant for
 compound objects (objects that contain other objects, like lists or
@@ -51,6 +51,7 @@ __getstate__() and __setstate__().  See the documentation for module
 # XXX need to support copy_reg here too...
 
 import types
+from pickle import _slotnames
 
 class Error(Exception):
     pass
@@ -61,7 +62,7 @@ try:
 except ImportError:
     PyStringMap = None
 
-__all__ = ["Error", "error", "copy", "deepcopy"]
+__all__ = ["Error", "copy", "deepcopy"]
 
 def copy(x):
     """Shallow copy operation on arbitrary Python objects.
@@ -76,18 +77,60 @@ def copy(x):
             copier = x.__copy__
         except AttributeError:
             try:
-                reductor = x.__reduce__
+                reductor = x.__class__.__reduce__
+                if reductor == object.__reduce__:
+                    reductor = _better_reduce
             except AttributeError:
-                raise error, \
-                      "un(shallow)copyable object of type %s" % type(x)
+                raise Error("un(shallow)copyable object of type %s" % type(x))
             else:
-                y = _reconstruct(x, reductor(), 0)
+                y = _reconstruct(x, reductor(x), 0)
         else:
             y = copier()
     else:
         y = copierfunction(x)
     return y
 
+def __newobj__(cls, *args):
+    return cls.__new__(cls, *args)
+
+def _better_reduce(obj):
+    cls = obj.__class__
+    getnewargs = getattr(obj, "__getnewargs__", None)
+    if getnewargs:
+        args = getnewargs()
+    else:
+        args = ()
+    getstate = getattr(obj, "__getstate__", None)
+    if getstate:
+        try:
+            state = getstate()
+        except TypeError, err:
+            # XXX Catch generic exception caused by __slots__
+            if str(err) != ("a class that defines __slots__ "
+                            "without defining __getstate__ "
+                            "cannot be pickled"):
+                raise # Not that specific exception
+            getstate = None
+    if not getstate:
+        state = getattr(obj, "__dict__", None)
+        names = _slotnames(cls)
+        if names:
+            slots = {}
+            nil = []
+            for name in names:
+                value = getattr(obj, name, nil)
+                if value is not nil:
+                    slots[name] = value
+            if slots:
+                state = (state, slots)
+    listitems = dictitems = None
+    if isinstance(obj, list):
+        listitems = iter(obj)
+    elif isinstance(obj, dict):
+        dictitems = obj.iteritems()
+    return __newobj__, (cls, args), state, listitems, dictitems
+    
+
 _copy_dispatch = d = {}
 
 def _copy_atomic(x):
@@ -175,12 +218,14 @@ def deepcopy(x, memo = None):
                 copier = x.__deepcopy__
             except AttributeError:
                 try:
-                    reductor = x.__reduce__
+                    reductor = x.__class__.__reduce__
+                    if reductor == object.__reduce__:
+                        reductor = _better_reduce
                 except AttributeError:
-                    raise error, \
-                       "un-deep-copyable object of type %s" % type(x)
+                    raise Error("un(shallow)copyable object of type %s" %
+                                type(x))
                 else:
-                    y = _reconstruct(x, reductor(), 1, memo)
+                    y = _reconstruct(x, reductor(x), 1, memo)
             else:
                 y = copier(memo)
     else:
@@ -331,7 +376,15 @@ def _reconstruct(x, info, deep, memo=None):
         if hasattr(y, '__setstate__'):
             y.__setstate__(state)
         else:
-            y.__dict__.update(state)
+            if isinstance(state, tuple) and len(state) == 2:
+                state, slotstate = state
+            else:
+                slotstate = None
+            if state is not None:
+                y.__dict__.update(state)
+            if slotstate is not None:
+                for key, value in slotstate.iteritems():
+                    setattr(y, key, value)
     return y
 
 del d

Lib/test/test_copy.py

@@ -41,11 +41,13 @@ class TestCopy(unittest.TestCase):
         self.assert_(y is x)
 
     def test_copy_cant(self):
-        class C(object):
+        class Meta(type):
             def __getattribute__(self, name):
                 if name == "__reduce__":
                     raise AttributeError, name
                 return object.__getattribute__(self, name)
+        class C:
+            __metaclass__ = Meta
         x = C()
         self.assertRaises(copy.Error, copy.copy, x)
 
@@ -189,11 +191,13 @@ class TestCopy(unittest.TestCase):
         self.assert_(y is x)
 
     def test_deepcopy_cant(self):
-        class C(object):
+        class Meta(type):
             def __getattribute__(self, name):
                 if name == "__reduce__":
                     raise AttributeError, name
                 return object.__getattribute__(self, name)
+        class C:
+            __metaclass__ = Meta
         x = C()
         self.assertRaises(copy.Error, copy.deepcopy, x)
 
@@ -411,6 +415,45 @@ class TestCopy(unittest.TestCase):
         self.assert_(x is not y)
         self.assert_(x["foo"] is not y["foo"])
 
+    def test_copy_slots(self):
+        class C(object):
+            __slots__ = ["foo"]
+        x = C()
+        x.foo = [42]
+        y = copy.copy(x)
+        self.assert_(x.foo is y.foo)
+
+    def test_deepcopy_slots(self):
+        class C(object):
+            __slots__ = ["foo"]
+        x = C()
+        x.foo = [42]
+        y = copy.deepcopy(x)
+        self.assertEqual(x.foo, y.foo)
+        self.assert_(x.foo is not y.foo)
+
+    def test_copy_list_subclass(self):
+        class C(list):
+            pass
+        x = C([[1, 2], 3])
+        x.foo = [4, 5]
+        y = copy.copy(x)
+        self.assertEqual(list(x), list(y))
+        self.assertEqual(x.foo, y.foo)
+        self.assert_(x[0] is y[0])
+        self.assert_(x.foo is y.foo)
+
+    def test_deepcopy_list_subclass(self):
+        class C(list):
+            pass
+        x = C([[1, 2], 3])
+        x.foo = [4, 5]
+        y = copy.deepcopy(x)
+        self.assertEqual(list(x), list(y))
+        self.assertEqual(x.foo, y.foo)
+        self.assert_(x[0] is not y[0])
+        self.assert_(x.foo is not y.foo)
+
 def test_main():
     suite = unittest.TestSuite()
     suite.addTest(unittest.makeSuite(TestCopy))