workaround missing dictproxy methods Fixes benjaminp#295

six.py

@@ -597,6 +597,8 @@ def iterlists(d, **kw):
 
     viewitems = operator.methodcaller("items")
 else:
+    import collections as _collections
+
     def iterkeys(d, **kw):
         return d.iterkeys(**kw)
 
@@ -609,11 +611,27 @@ def iteritems(d, **kw):
     def iterlists(d, **kw):
         return d.iterlists(**kw)
 
-    viewkeys = operator.methodcaller("viewkeys")
-
-    viewvalues = operator.methodcaller("viewvalues")
+    def viewkeys(d):
+        return (
+            _collections.KeysView(d)
+            if isinstance(d, types.DictProxyType)
+            else d.viewkeys()
+        )
+
+    def viewvalues(d):
+        return (
+            _collections.ValuesView(d)
+            if isinstance(d, types.DictProxyType)
+            else d.viewvalues()
+        )
+
+    def viewitems(d):
+        return (
+            _collections.ItemsView(d)
+            if isinstance(d, types.DictProxyType)
+            else d.viewitems()
+        )
 
-    viewitems = operator.methodcaller("viewitems")
 
 _add_doc(iterkeys, "Return an iterator over the keys of a dictionary.")
 _add_doc(itervalues, "Return an iterator over the values of a dictionary.")

test_six.py

@@ -434,6 +434,33 @@ def stock_method_name(viewwhat):
         view = meth(d)
         assert set(view) == set(getattr(d, name)())
 
+@pytest.mark.skipif("sys.version_info[:2] < (2, 7)",
+                reason="view methods on dictionaries only available on 2.7+")
+def test_dictproxy_views():
+    class Ham(object):
+        pass
+
+    dictproxy = vars(Ham)
+    dictcopy = dict(dictproxy)
+
+    fns = [six.viewkeys, six.viewvalues, six.viewitems]
+    dictproxy_views = [fn(dictproxy) for fn in fns]
+
+    # test dictproxy six.view*s work the same as per a regular dict
+    assert (
+        [set(v) for v in dictproxy_views]
+        == [set(fn(dictcopy)) for fn in fns]
+    )
+
+    # test that dictproxy mutations are also exposed on the relevent
+    # six.view*s results
+    eggs = object()
+    setattr(Ham, "spam", eggs)
+    keysview, valuesview, itemsview = dictproxy_views
+    assert "spam" in keysview
+    assert eggs in valuesview
+    assert ("spam", eggs) in itemsview
+
 
 def test_advance_iterator():
     assert six.next is six.advance_iterator