Merge pull request #5477 from jreback/is_copy_bug

API: make sure _is_copy on NDFrame is always available (GH5475)

Author: jreback

pandas/core/generic.py

@@ -74,6 +74,7 @@ class NDFrame(PandasObject):
         '_data', 'name', '_cacher', '_is_copy', '_subtyp', '_index', '_default_kind', '_default_fill_value']
     _internal_names_set = set(_internal_names)
     _metadata = []
+    _is_copy = None
 
     def __init__(self, data, axes=None, copy=False, dtype=None, fastpath=False):
 

pandas/tests/test_indexing.py

@@ -1736,6 +1736,16 @@ def f():
         df = DataFrame({'A':['aaa','bbb','ccc'],'B':[1,2,3]})
         df.loc[0]['A'] = 111
 
+        # make sure that _is_copy is picked up reconstruction
+        # GH5475
+        df = DataFrame({"A": [1,2]})
+        self.assert_(df._is_copy is False)
+        with tm.ensure_clean('__tmp__pickle') as path:
+            df.to_pickle(path)
+            df2 = pd.read_pickle(path)
+            df2["B"] = df2["A"]
+            df2["B"] = df2["A"]
+
     def test_floating_index_doc_example(self):
 
         index = Index([1.5, 2, 3, 4.5, 5])