Inplace

pandas/core/frame.py

@@ -2610,7 +2610,7 @@ def fillna(self, value=None, method='pad', axis=0, inplace=False,
     #----------------------------------------------------------------------
     # Rename
 
-    def rename(self, index=None, columns=None, copy=True):
+    def rename(self, index=None, columns=None, copy=True, inplace=False):
         """
         Alter index and / or columns using input function or
         functions. Function / dict values must be unique (1-to-1). Labels not
@@ -2624,6 +2624,9 @@ def rename(self, index=None, columns=None, copy=True):
             Transformation to apply to column values
         copy : boolean, default True
             Also copy underlying data
+        inplace : boolean, default False
+            Whether to return a new DataFrame. If True then value of copy is
+            ignored.
 
         See also
         --------
@@ -2643,7 +2646,7 @@ def rename(self, index=None, columns=None, copy=True):
 
         self._consolidate_inplace()
 
-        result = self.copy(deep=copy)
+        result = self if inplace else self.copy(deep=copy)
 
         if index is not None:
             result._rename_index_inplace(index_f)

pandas/core/internals.py

@@ -103,18 +103,22 @@ def merge(self, other):
         return _merge_blocks([self, other], self.ref_items)
 
     def reindex_axis(self, indexer, mask, needs_masking, axis=0,
-                     fill_value=np.nan):
+                     fill_value=np.nan, out=None):
         """
         Reindex using pre-computed indexer information
         """
         if self.values.size > 0:
             new_values = com.take_fast(self.values, indexer, mask,
                                        needs_masking, axis=axis,
-                                       fill_value=fill_value)
+                                       fill_value=fill_value,
+                                       out=out)
         else:
             shape = list(self.shape)
             shape[axis] = len(indexer)
-            new_values = np.empty(shape)
+            if out is not None and (out.shape == shape):
+                new_values = out
+            else:
+                new_values = np.empty(shape)
             new_values.fill(fill_value)
         return make_block(new_values, self.items, self.ref_items)
 

pandas/core/series.py

@@ -2377,7 +2377,7 @@ def interpolate(self, method='linear'):
 
         return Series(result, index=self.index, name=self.name)
 
-    def rename(self, mapper):
+    def rename(self, mapper, inplace=False):
         """
         Alter Series index using dict or function
 
@@ -2412,7 +2412,7 @@ def rename(self, mapper):
         renamed : Series (new object)
         """
         mapper_f = _get_rename_function(mapper)
-        result = self.copy()
+        result = self if inplace else self.copy()
         result.index = [mapper_f(x) for x in self.index]
 
         return result

pandas/tests/test_frame.py

@@ -3807,6 +3807,15 @@ def test_rename_nocopy(self):
         renamed['foo'] = 1.
         self.assert_((self.frame['C'] == 1.).all())
 
+    def test_rename_inplace(self):
+        self.frame.rename(columns={'C' : 'foo'})
+        self.assert_('C' in self.frame)
+        self.assert_('foo' not in self.frame)
+
+        self.frame.rename(columns={'C' : 'foo'}, inplace=True)
+        self.assert_('C' not in self.frame)
+        self.assert_('foo' in self.frame)
+
     #----------------------------------------------------------------------
     # Time series related
 

pandas/tests/test_series.py

@@ -2374,6 +2374,12 @@ def test_rename(self):
         renamed = s.rename({'b' : 'foo', 'd' : 'bar'})
         self.assert_(np.array_equal(renamed.index, ['a', 'foo', 'c', 'bar']))
 
+    def test_rename_inplace(self):
+        renamer = lambda x: x.strftime('%Y%m%d')
+        expected = renamer(self.ts.index[0])
+        self.ts.rename(renamer, inplace=True)
+        self.assertEqual(self.ts.index[0], expected)
+
     def test_preserveRefs(self):
         seq = self.ts[[5,10,15]]
         seq[1] = np.NaN