BUG: (GH3880) index names are now propogated with loc/ix

RELEASE.rst

@@ -177,6 +177,8 @@ pandas 0.11.1
     - Non-unique indexing with a slice via ``loc`` and friends fixed (GH3659_)
     - Allow insert/delete to non-unique columns (GH3679_)
     - Extend ``reindex`` to correctly deal with non-unique indices (GH3679_)
+    - ``DataFrame.itertuples()`` now works with frames with duplicate column
+      names (GH3873_)
   - Fixed bug in groupby with empty series referencing a variable before assignment. (GH3510_)
   - Fixed bug in mixed-frame assignment with aligned series (GH3492_)
   - Fixed bug in selecting month/quarter/year from a series would not select the time element
@@ -228,8 +230,7 @@ pandas 0.11.1
   - PandasObjects raise TypeError when trying to hash (GH3882_)
   - Fix incorrect arguments passed to concat that are not list-like (e.g. concat(df1,df2)) (GH3481_)
   - Correctly parse when passed the ``dtype=str`` (or other variable-len string dtypes) in ``read_csv`` (GH3795_)
-  - ``DataFrame.itertuples()`` now works with frames with duplicate column
-    names (GH3873_)
+  - Fix index name not propogating when using ``loc/ix`` (GH3880_)
 
 .. _GH3164: https://github.com/pydata/pandas/issues/3164
 .. _GH2786: https://github.com/pydata/pandas/issues/2786
@@ -323,6 +324,7 @@ pandas 0.11.1
 .. _GH3834: https://github.com/pydata/pandas/issues/3834
 .. _GH3873: https://github.com/pydata/pandas/issues/3873
 .. _GH3877: https://github.com/pydata/pandas/issues/3877
+.. _GH3880: https://github.com/pydata/pandas/issues/3880
 
 
 pandas 0.11.0

doc/source/v0.11.1.txt

@@ -348,11 +348,14 @@ Bug Fixes
     - Duplicate indexes with and empty DataFrame.from_records will return a correct frame (GH3562_)
     - Concat to produce a non-unique columns when duplicates are across dtypes is fixed (GH3602_)
     - Allow insert/delete to non-unique columns (GH3679_)
+    - Non-unique indexing with a slice via ``loc`` and friends fixed (GH3659_)
+    - Allow insert/delete to non-unique columns (GH3679_)
+    - Extend ``reindex`` to correctly deal with non-unique indices (GH3679_)
+    - ``DataFrame.itertuples()`` now works with frames with duplicate column
+      names (GH3873_)
 
   - ``DataFrame.from_records`` did not accept empty recarrays (GH3682_)
   - ``read_html`` now correctly skips tests (GH3741_)
-  - ``DataFrame.itertuples()`` now works with frames with duplicate column
-    names (GH3873_)
 
 See the `full release notes
 <https://github.com/pydata/pandas/blob/master/RELEASE.rst>`__ or issue tracker
@@ -405,3 +408,5 @@ on GitHub for a complete list.
 .. _GH3834: https://github.com/pydata/pandas/issues/3834
 .. _GH3873: https://github.com/pydata/pandas/issues/3873
 .. _GH3877: https://github.com/pydata/pandas/issues/3877
+.. _GH3659: https://github.com/pydata/pandas/issues/3659
+.. _GH3679: https://github.com/pydata/pandas/issues/3679

pandas/core/frame.py

@@ -2712,14 +2712,14 @@ def _reindex_multi(self, new_index, new_columns, copy, fill_value):
     def _reindex_index(self, new_index, method, copy, level, fill_value=NA,
                        limit=None):
         new_index, indexer = self.index.reindex(new_index, method, level,
-                                                limit=limit)
+                                                limit=limit, copy_if_needed=True)
         return self._reindex_with_indexers(new_index, indexer, None, None,
                                            copy, fill_value)
 
     def _reindex_columns(self, new_columns, copy, level, fill_value=NA,
                          limit=None):
         new_columns, indexer = self.columns.reindex(new_columns, level=level,
-                                                    limit=limit)
+                                                    limit=limit, copy_if_needed=True)
         return self._reindex_with_indexers(None, None, new_columns, indexer,
                                            copy, fill_value)
 

pandas/core/index.py

@@ -920,7 +920,7 @@ def _get_method(self, method):
         }
         return aliases.get(method, method)
 
-    def reindex(self, target, method=None, level=None, limit=None):
+    def reindex(self, target, method=None, level=None, limit=None, copy_if_needed=False):
         """
         For Index, simply returns the new index and the results of
         get_indexer. Provided here to enable an interface that is amenable for
@@ -939,6 +939,12 @@ def reindex(self, target, method=None, level=None, limit=None):
         else:
             if self.equals(target):
                 indexer = None
+
+                # to avoid aliasing an existing index
+                if copy_if_needed and target.name != self.name and self.name is not None:
+                    if target.name is None:
+                        target = self.copy()
+
             else:
                 if self.is_unique:
                     indexer = self.get_indexer(target, method=method,
@@ -2196,7 +2202,7 @@ def get_indexer(self, target, method=None, limit=None):
 
         return com._ensure_platform_int(indexer)
 
-    def reindex(self, target, method=None, level=None, limit=None):
+    def reindex(self, target, method=None, level=None, limit=None, copy_if_needed=False):
         """
         Performs any necessary conversion on the input index and calls
         get_indexer. This method is here so MultiIndex and an Index of

pandas/core/internals.py

@@ -1948,7 +1948,7 @@ def reindex_axis(self, new_axis, method=None, axis=0, copy=True):
                                      'axis == 0')
             return self.reindex_items(new_axis)
 
-        new_axis, indexer = cur_axis.reindex(new_axis, method)
+        new_axis, indexer = cur_axis.reindex(new_axis, method, copy_if_needed=True)
         return self.reindex_indexer(new_axis, indexer, axis=axis)
 
     def reindex_indexer(self, new_axis, indexer, axis=1, fill_value=np.nan):
@@ -2014,7 +2014,7 @@ def reindex_items(self, new_items, copy=True, fill_value=np.nan):
             return data.reindex_items(new_items)
 
         # TODO: this part could be faster (!)
-        new_items, indexer = self.items.reindex(new_items)
+        new_items, indexer = self.items.reindex(new_items, copy_if_needed=True)
         new_axes = [new_items] + self.axes[1:]
 
         # could have so me pathological (MultiIndex) issues here

pandas/tests/test_frame.py

@@ -7207,6 +7207,7 @@ def test_reindex_name_remains(self):
         s = Series(random.rand(10))
         df = DataFrame(s, index=np.arange(len(s)))
         i = Series(np.arange(10), name='iname')
+
         df = df.reindex(i)
         self.assert_(df.index.name == 'iname')
 

pandas/tests/test_indexing.py

@@ -1024,6 +1024,19 @@ def test_non_unique_loc(self):
         expected = DataFrame({'A' : [2,4,5], 'B' : [4,6,7]}, index = [1,1,2])
         assert_frame_equal(result,expected)
 
+    def test_loc_name(self):
+        # GH 3880
+        df = DataFrame([[1, 1], [1, 1]])
+        df.index.name = 'index_name'
+        result = df.iloc[[0, 1]].index.name
+        self.assert_(result == 'index_name')
+
+        result = df.ix[[0, 1]].index.name
+        self.assert_(result == 'index_name')
+
+        result = df.loc[[0, 1]].index.name
+        self.assert_(result == 'index_name')
+
 if __name__ == '__main__':
     import nose
     nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure'],