Merge pull request pandas-dev#3212 from wesm/inplace-not-return-self

API: return None when inplace=True. closes pandas-dev#1893

Author: wesm

RELEASE.rst

@@ -158,6 +158,7 @@ pandas 0.11.0
   - util.testing.assert_frame_equal now checks the column and index names (GH2964_)
   - Constructors will now return a more informative ValueError on failures
     when invalid shapes are passed
+  - Methods return None when inplace=True (GH1893_)
 
 **Bug Fixes**
 
@@ -259,6 +260,7 @@ pandas 0.11.0
 
 .. _GH622: https://github.com/pydata/pandas/issues/622
 .. _GH797: https://github.com/pydata/pandas/issues/797
+.. _GH1893: https://github.com/pydata/pandas/issues/1893
 .. _GH1978: https://github.com/pydata/pandas/issues/1978
 .. _GH2758: https://github.com/pydata/pandas/issues/2758
 .. _GH2121: https://github.com/pydata/pandas/issues/2121

pandas/core/frame.py

@@ -2708,16 +2708,9 @@ def set_index(self, keys, drop=True, append=False, inplace=False,
 
         frame.index = index
 
-        if inplace:
-            import warnings
-            warnings.warn("set_index with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
-        else:
+        if not inplace:
             return frame
 
-        return frame if not inplace else None
-
     def reset_index(self, level=None, drop=False, inplace=False, col_level=0,
                     col_fill=''):
         """
@@ -2815,12 +2808,7 @@ def _maybe_cast(values):
             new_obj.insert(0, name, _maybe_cast(values))
 
         new_obj.index = new_index
-        if inplace:
-            import warnings
-            warnings.warn("reset_index with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
-        else:
+        if not inplace:
             return new_obj
 
     delevel = deprecate('delevel', reset_index)
@@ -2988,10 +2976,6 @@ def drop_duplicates(self, cols=None, take_last=False, inplace=False):
             inds, = (-duplicated).nonzero()
             self._data = self._data.take(inds)
             self._clear_item_cache()
-            import warnings
-            warnings.warn("drop_duplicates with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
         else:
             return self[-duplicated]
 
@@ -3147,10 +3131,6 @@ def sort_index(self, axis=0, by=None, ascending=True, inplace=False):
                 self._data = self._data.take(indexer)
 
             self._clear_item_cache()
-            import warnings
-            warnings.warn("sort/sort_index with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
         else:
             return self.take(indexer, axis=axis, convert=False)
 
@@ -3194,10 +3174,6 @@ def sortlevel(self, level=0, axis=0, ascending=True, inplace=False):
                 self._data = self._data.take(indexer)
 
             self._clear_item_cache()
-            import warnings
-            warnings.warn("sortlevel with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
         else:
             return self.take(indexer, axis=axis, convert=False)
 
@@ -3328,10 +3304,6 @@ def fillna(self, value=None, method=None, axis=0, inplace=False,
 
         if inplace:
             self._data = new_data
-            import warnings
-            warnings.warn("fillna with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
         else:
             return self._constructor(new_data)
 
@@ -3380,10 +3352,6 @@ def replace(self, to_replace, value=None, method='pad', axis=0,
         self._consolidate_inplace()
 
         axis = self._get_axis_number(axis)
-        if inplace:
-            import warnings
-            warnings.warn("replace with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
 
         if value is None:
             return self._interpolate(to_replace, method, axis, inplace, limit)
@@ -3397,13 +3365,17 @@ def replace(self, to_replace, value=None, method='pad', axis=0,
                     new_data = self._data
                     for c, src in to_replace.iteritems():
                         if c in value and c in self:
-                            new_data = new_data.replace(src, value[c], filter = [ c ], inplace=inplace)
+                            new_data = new_data.replace(src, value[c],
+                                                        filter=[ c ],
+                                                        inplace=inplace)
 
                 elif not isinstance(value, (list, np.ndarray)):
                     new_data = self._data
                     for k, src in to_replace.iteritems():
                         if k in self:
-                            new_data = new_data.replace(src, value, filter = [ k ], inplace=inplace)
+                            new_data = new_data.replace(src, value,
+                                                        filter = [ k ],
+                                                        inplace=inplace)
                 else:
                     raise ValueError('Fill value must be scalar or dict or Series')
 
@@ -3430,7 +3402,9 @@ def replace(self, to_replace, value=None, method='pad', axis=0,
                     new_data = self._data
                     for k, v in value.iteritems():
                         if k in self:
-                            new_data = new_data.replace(to_replace, v, filter = [ k ], inplace=inplace)
+                            new_data = new_data.replace(to_replace, v,
+                                                        filter=[ k ],
+                                                        inplace=inplace)
 
                 elif not isinstance(value, (list, np.ndarray)):  # NA -> 0
                     new_data = self._data.replace(to_replace, value,
@@ -3442,7 +3416,6 @@ def replace(self, to_replace, value=None, method='pad', axis=0,
 
         if inplace:
             self._data = new_data
-            return self
         else:
             return self._constructor(new_data)
 
@@ -3525,12 +3498,7 @@ def rename(self, index=None, columns=None, copy=True, inplace=False):
         if columns is not None:
             result._rename_columns_inplace(columns_f)
 
-        if inplace:
-            import warnings
-            warnings.warn("rename with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
-        else:
+        if not inplace:
             return result
 
     def _rename_index_inplace(self, mapper):

pandas/core/series.py

@@ -122,7 +122,7 @@ def convert_to_array(values):
 
             # 2 datetimes or 2 timedeltas
             if (is_timedelta_lhs and is_timedelta_rhs) or (is_datetime_lhs and is_datetime_rhs):
-                
+
                 dtype = 'timedelta64[ns]'
 
                 # we may have to convert to object unfortunately here
@@ -601,7 +601,7 @@ def _is_mixed_type(self):
     def _slice(self, slobj, axis=0, raise_on_error=False):
         if raise_on_error:
             _check_slice_bounds(slobj, self.values)
-            
+
         return self._constructor(self.values[slobj], index=self.index[slobj])
 
     def __getitem__(self, key):
@@ -1047,11 +1047,6 @@ def reset_index(self, level=None, drop=False, name=None, inplace=False):
                 self.index = new_index
                 # set name if it was passed, otherwise, keep the previous name
                 self.name = name or self.name
-                import warnings
-                warnings.warn("Series.reset_index with inplace=True will "
-                              "return None from pandas 0.11 onward",
-                              FutureWarning)
-                return self
             else:
                 return Series(self.values.copy(), index=new_index,
                               name=self.name)
@@ -2615,13 +2610,8 @@ def fillna(self, value=None, method=None, inplace=False,
         -------
         filled : Series
         """
-        if inplace:
-            import warnings
-            warnings.warn("Series.fillna with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-
         if not self._can_hold_na:
-            return self.copy() if not inplace else self
+            return self.copy() if not inplace else None
 
         if value is not None:
             if method is not None:
@@ -2647,9 +2637,7 @@ def fillna(self, value=None, method=None, inplace=False,
             else:
                 result = Series(values, index=self.index, name=self.name)
 
-        if inplace:
-            return self
-        else:
+        if not inplace:
             return result
 
     def ffill(self, inplace=False, limit=None):
@@ -2756,12 +2744,7 @@ def _rep_dict(rs, to_rep):  # replace {[src] -> dest}
             raise ValueError('Unrecognized to_replace type %s' %
                              type(to_replace))
 
-        if inplace:
-            import warnings
-            warnings.warn("Series.replace with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
-        else:
+        if not inplace:
             return result
 
     def isin(self, values):
@@ -3110,12 +3093,7 @@ def rename(self, mapper, inplace=False):
         result = self if inplace else self.copy()
         result.index = Index([mapper_f(x) for x in self.index], name=self.index.name)
 
-        if inplace:
-            import warnings
-            warnings.warn("Series.rename with inplace=True  will return None"
-                          " from pandas 0.11 onward", FutureWarning)
-            return self
-        else:
+        if not inplace:
             return result
 
     @property

pandas/tests/test_frame.py

@@ -9476,15 +9476,15 @@ def test_strange_column_corruption_issue(self):
         self.assertTrue(first == second == 0)
 
     def test_inplace_return_self(self):
-        # re #1893, TODO: remove in 0.11
+        # re #1893
 
         data = DataFrame({'a': ['foo', 'bar', 'baz', 'qux'],
                           'b': [0, 0, 1, 1],
                           'c': [1, 2, 3, 4]})
 
         def _check_f(base, f):
             result = f(base)
-            self.assertTrue(result is base)
+            self.assertTrue(result is None)
 
         # -----DataFrame-----