Inplace in more places

pandas/core/frame.py

@@ -2335,7 +2335,7 @@ def set_index(self, keys, drop=True, append=False, inplace=False,
         frame.index = index
         return frame
 
-    def reset_index(self, level=None, drop=False):
+    def reset_index(self, level=None, drop=False, inplace=False):
         """
         For DataFrame with multi-level index, return new DataFrame with
         labeling information in the columns under the index names, defaulting
@@ -2350,12 +2350,17 @@ def reset_index(self, level=None, drop=False):
             default
         drop : boolean, default False
             Do not try to insert index into dataframe columns
+        inplace : boolean, default False
+            Modify the DataFrame in place (do not create a new object)
 
         Returns
         -------
         resetted : DataFrame
         """
-        new_obj = self.copy()
+        if inplace:
+            new_obj  = self
+        else:
+            new_obj = self.copy()
 
         def _maybe_cast(values):
             if values.dtype == np.object_:

pandas/core/series.py

@@ -750,7 +750,7 @@ def set_value(self, label, value):
             new_values = np.concatenate([self.values, [value]])
             return Series(new_values, index=new_index, name=self.name)
 
-    def reset_index(self, drop=False, name=None):
+    def reset_index(self, drop=False, name=None, inplace=False):
         """
         Analagous to the DataFrame.reset_index function, see docstring there.
 
@@ -760,13 +760,21 @@ def reset_index(self, drop=False, name=None):
             Do not try to insert index into dataframe columns
         name : object, default None
             The name of the column corresponding to the Series values
+        inplace : boolean, default False
+            Modify the Series in place (do not create a new object)
 
         Returns
         ----------
         resetted : DataFrame, or Series if drop == True
         """
         if drop:
-            return Series(self, index=np.arange(len(self)), name=self.name)
+            if inplace:
+                self.index = np.arange(len(self))
+                # set name if it was passed, otherwise, keep the previous name
+                self.name = name or self.name
+                return self
+            else:
+                return Series(self, index=np.arange(len(self)), name=self.name)
         else:
             from pandas.core.frame import DataFrame
             if name is None:

pandas/tests/test_frame.py

@@ -6273,6 +6273,12 @@ def test_reset_index(self):
         xp = self.frame.reset_index().set_index(['index', 'B'])
         assert_frame_equal(rs, xp)
 
+        #test resetting in place
+        df = self.frame.copy()
+        resetted = self.frame.reset_index()
+        df.reset_index(inplace=True)
+        assert_frame_equal(df, resetted)
+
     def test_reset_index_right_dtype(self):
         time = np.arange(0.0, 10, np.sqrt(2)/2)
         s1 = Series((9.81 * time ** 2) /2,

pandas/tests/test_series.py

@@ -2964,6 +2964,12 @@ def test_reset_index(self):
         df = ser.reset_index(name='value2')
         self.assert_('value2' in df)
 
+        #check inplace
+        s = ser.reset_index(drop=True)
+        s2 = ser
+        s2.reset_index(drop=True, inplace=True)
+        assert_series_equal(s, s2)
+
     def test_timeseries_coercion(self):
         idx = tm.makeDateIndex(10000)
         ser = Series(np.random.randn(len(idx)), idx.astype(object))