bpo-26579: Add object.__getstate__(). (GH-2821)

Copying and pickling instances of subclasses of builtin types
bytearray, set, frozenset, collections.OrderedDict, collections.deque,
weakref.WeakSet, and datetime.tzinfo now copies and pickles instance attributes
implemented as slots.

1 files changed, 16 insertions, 4 deletions

diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
index 264435c..7af8dcd 100644
--- a/Lib/collections/__init__.py
+++ b/Lib/collections/__init__.py
@@ -271,10 +271,22 @@ class OrderedDict(dict):
 
     def __reduce__(self):
         'Return state information for pickling'
-        inst_dict = vars(self).copy()
-        for k in vars(OrderedDict()):
-            inst_dict.pop(k, None)
-        return self.__class__, (), inst_dict or None, None, iter(self.items())
+        state = self.__getstate__()
+        if state:
+            if isinstance(state, tuple):
+                state, slots = state
+            else:
+                slots = {}
+            state = state.copy()
+            slots = slots.copy()
+            for k in vars(OrderedDict()):
+                state.pop(k, None)
+                slots.pop(k, None)
+            if slots:
+                state = state, slots
+            else:
+                state = state or None
+        return self.__class__, (), state, None, iter(self.items())
 
     def copy(self):
         'od.copy() -> a shallow copy of od'