API: Index.take inconsistently handle fill_value

doc/source/whatsnew/v0.18.1.txt

@@ -29,7 +29,6 @@ New features
 Enhancements
 ~~~~~~~~~~~~
 
-
 .. _whatsnew_0181.partial_string_indexing:
 
 Partial string indexing on ``DateTimeIndex`` when part of a ``MultiIndex``
@@ -59,6 +58,14 @@ Other Enhancements
 - ``pd.read_csv()`` now supports opening ZIP files that contains a single CSV, via extension inference or explict ``compression='zip'`` (:issue:`12175`)
 - ``pd.read_csv()`` now supports opening files using xz compression, via extension inference or explicit ``compression='xz'`` is specified; ``xz`` compressions is also supported by ``DataFrame.to_csv`` in the same way (:issue:`11852`)
 - ``pd.read_msgpack()`` now always gives writeable ndarrays even when compression is used (:issue:`12359`).
+- ``Index.take`` now handles ``allow_fill`` and ``fill_value`` consistently (:issue:`12631`)
+
+.. ipython:: python
+
+   idx = pd.Index([1., 2., 3., 4.], dtype='float')
+   idx.take([2, -1])     # default, allow_fill=True, fill_value=None
+   idx.take([2, -1], fill_value=True)
+
 
 .. _whatsnew_0181.api:
 

pandas/indexes/base.py

@@ -1329,24 +1329,60 @@ def _ensure_compat_concat(indexes):
 
         return indexes
 
-    def take(self, indices, axis=0, allow_fill=True, fill_value=None):
-        """
-        return a new Index of the values selected by the indexer
+    _index_shared_docs['take'] = """
+        return a new Index of the values selected by the indices
 
         For internal compatibility with numpy arrays.
 
-        # filling must always be None/nan here
-        # but is passed thru internally
+        Parameters
+        ----------
+        indices : list
+            Indices to be taken
+        axis : int, optional
+            The axis over which to select values, always 0.
+        allow_fill : bool, default True
+        fill_value : bool, default None
+            If allow_fill=True and fill_value is not None, indices specified by
+            -1 is regarded as NA. If Index doesn't hold NA, raise ValueError
 
         See also
         --------
         numpy.ndarray.take
         """
-
+    @Appender(_index_shared_docs['take'])
+    def take(self, indices, axis=0, allow_fill=True, fill_value=None):
         indices = com._ensure_platform_int(indices)
-        taken = self.values.take(indices)
+        if self._can_hold_na:
+            taken = self._assert_take_fillable(self.values, indices,
+                                               allow_fill=allow_fill,
+                                               fill_value=fill_value,
+                                               na_value=self._na_value)
+        else:
+            if allow_fill and fill_value is not None:
+                msg = 'Unable to fill values because {0} cannot contain NA'
+                raise ValueError(msg.format(self.__class__.__name__))
+            taken = self.values.take(indices)
         return self._shallow_copy(taken)
 
+    def _assert_take_fillable(self, values, indices, allow_fill=True,
+                              fill_value=None, na_value=np.nan):
+        """ Internal method to handle NA filling of take """
+        indices = com._ensure_platform_int(indices)
+
+        # only fill if we are passing a non-None fill_value
+        if allow_fill and fill_value is not None:
+            if (indices < -1).any():
+                msg = ('When allow_fill=True and fill_value is not None, '
+                       'all indices must be >= -1')
+                raise ValueError(msg)
+            taken = values.take(indices)
+            mask = indices == -1
+            if mask.any():
+                taken[mask] = na_value
+        else:
+            taken = values.take(indices)
+        return taken
+
     @cache_readonly
     def _isnan(self):
         """ return if each value is nan"""

pandas/indexes/category.py

@@ -459,21 +459,13 @@ def _convert_list_indexer(self, keyarr, kind=None):
 
         return None
 
-    def take(self, indexer, axis=0, allow_fill=True, fill_value=None):
-        """
-        For internal compatibility with numpy arrays.
-
-        # filling must always be None/nan here
-        # but is passed thru internally
-        assert isnull(fill_value)
-
-        See also
-        --------
-        numpy.ndarray.take
-        """
-
-        indexer = com._ensure_platform_int(indexer)
-        taken = self.codes.take(indexer)
+    @Appender(_index_shared_docs['take'])
+    def take(self, indices, axis=0, allow_fill=True, fill_value=None):
+        indices = com._ensure_platform_int(indices)
+        taken = self._assert_take_fillable(self.codes, indices,
+                                           allow_fill=allow_fill,
+                                           fill_value=fill_value,
+                                           na_value=-1)
         return self._create_from_codes(taken)
 
     def delete(self, loc):

pandas/indexes/multi.py

@@ -1,3 +1,4 @@
+
 # pylint: disable=E1101,E1103,W0232
 import datetime
 import warnings
@@ -11,7 +12,7 @@
 
 from pandas.compat import range, zip, lrange, lzip, map
 from pandas import compat
-from pandas.core.base import FrozenList
+from pandas.core.base import FrozenList, FrozenNDArray
 import pandas.core.base as base
 from pandas.util.decorators import (Appender, cache_readonly,
                                     deprecate, deprecate_kwarg)
@@ -1003,12 +1004,38 @@ def __getitem__(self, key):
                               names=self.names, sortorder=sortorder,
                               verify_integrity=False)
 
-    def take(self, indexer, axis=None):
-        indexer = com._ensure_platform_int(indexer)
-        new_labels = [lab.take(indexer) for lab in self.labels]
-        return MultiIndex(levels=self.levels, labels=new_labels,
+    @Appender(_index_shared_docs['take'])
+    def take(self, indices, axis=0, allow_fill=True, fill_value=None):
+        indices = com._ensure_platform_int(indices)
+        taken = self._assert_take_fillable(self.labels, indices,
+                                                allow_fill=allow_fill,
+                                                fill_value=fill_value,
+                                                na_value=-1)
+        return MultiIndex(levels=self.levels, labels=taken,
                           names=self.names, verify_integrity=False)
 
+    def _assert_take_fillable(self, values, indices, allow_fill=True,
+                              fill_value=None, na_value=None):
+        """ Internal method to handle NA filling of take """
+        # only fill if we are passing a non-None fill_value
+        if allow_fill and fill_value is not None:
+            if (indices < -1).any():
+                msg = ('When allow_fill=True and fill_value is not None, '
+                       'all indices must be >= -1')
+                raise ValueError(msg)
+            taken = [lab.take(indices) for lab in self.labels]
+            mask = indices == -1
+            if mask.any():
+                masked = []
+                for new_label in taken:
+                    label_values = new_label.values()
+                    label_values[mask] = na_value
+                    masked.append(base.FrozenNDArray(label_values))
+                taken = masked
+        else:
+            taken = [lab.take(indices) for lab in self.labels]
+        return taken
+
     def append(self, other):
         """
         Append a collection of Index options together

pandas/tests/indexes/test_base.py

@@ -1240,6 +1240,34 @@ def test_nan_first_take_datetime(self):
         exp = Index([idx[-1], idx[0], idx[1]])
         tm.assert_index_equal(res, exp)
 
+    def test_take_fill_value(self):
+        # GH 12631
+        idx = pd.Index(list('ABC'), name='xxx')
+        result = idx.take(np.array([1, 0, -1]))
+        expected = pd.Index(list('BAC'), name='xxx')
+        tm.assert_index_equal(result, expected)
+
+        # fill_value
+        result = idx.take(np.array([1, 0, -1]), fill_value=True)
+        expected = pd.Index(['B', 'A', np.nan], name='xxx')
+        tm.assert_index_equal(result, expected)
+
+        # allow_fill=False
+        result = idx.take(np.array([1, 0, -1]), allow_fill=False,
+                          fill_value=True)
+        expected = pd.Index(['B', 'A', 'C'], name='xxx')
+        tm.assert_index_equal(result, expected)
+
+        msg = ('When allow_fill=True and fill_value is not None, '
+               'all indices must be >= -1')
+        with tm.assertRaisesRegexp(ValueError, msg):
+            idx.take(np.array([1, 0, -2]), fill_value=True)
+        with tm.assertRaisesRegexp(ValueError, msg):
+            idx.take(np.array([1, 0, -5]), fill_value=True)
+
+        with tm.assertRaises(IndexError):
+            idx.take(np.array([1, -5]))
+
     def test_reindex_preserves_name_if_target_is_list_or_ndarray(self):
         # GH6552
         idx = pd.Index([0, 1, 2])

pandas/tests/indexes/test_category.py

@@ -708,3 +708,100 @@ def test_fillna_categorical(self):
         with tm.assertRaisesRegexp(ValueError,
                                    'fill value must be in categories'):
             idx.fillna(2.0)
+
+    def test_take_fill_value(self):
+        # GH 12631
+
+        # numeric category
+        idx = pd.CategoricalIndex([1, 2, 3], name='xxx')
+        result = idx.take(np.array([1, 0, -1]))
+        expected = pd.CategoricalIndex([2, 1, 3], name='xxx')
+        tm.assert_index_equal(result, expected)
+        tm.assert_categorical_equal(result.values, expected.values)
+
+        # fill_value
+        result = idx.take(np.array([1, 0, -1]), fill_value=True)
+        expected = pd.CategoricalIndex([2, 1, np.nan], categories=[1, 2, 3],
+                                       name='xxx')
+        tm.assert_index_equal(result, expected)
+        tm.assert_categorical_equal(result.values, expected.values)
+
+        # allow_fill=False
+        result = idx.take(np.array([1, 0, -1]), allow_fill=False,
+                          fill_value=True)
+        expected = pd.CategoricalIndex([2, 1, 3], name='xxx')
+        tm.assert_index_equal(result, expected)
+        tm.assert_categorical_equal(result.values, expected.values)
+
+        # object category
+        idx = pd.CategoricalIndex(list('CBA'), categories=list('ABC'),
+                                  ordered=True, name='xxx')
+        result = idx.take(np.array([1, 0, -1]))
+        expected = pd.CategoricalIndex(list('BCA'), categories=list('ABC'),
+                                       ordered=True, name='xxx')
+        tm.assert_index_equal(result, expected)
+        tm.assert_categorical_equal(result.values, expected.values)
+
+        # fill_value
+        result = idx.take(np.array([1, 0, -1]), fill_value=True)
+        expected = pd.CategoricalIndex(['B', 'C', np.nan],
+                                       categories=list('ABC'), ordered=True,
+                                       name='xxx')
+        tm.assert_index_equal(result, expected)
+        tm.assert_categorical_equal(result.values, expected.values)
+
+        # allow_fill=False
+        result = idx.take(np.array([1, 0, -1]), allow_fill=False,
+                          fill_value=True)
+        expected = pd.CategoricalIndex(list('BCA'), categories=list('ABC'),
+                                       ordered=True, name='xxx')
+        tm.assert_index_equal(result, expected)
+        tm.assert_categorical_equal(result.values, expected.values)
+
+        msg = ('When allow_fill=True and fill_value is not None, '
+               'all indices must be >= -1')
+        with tm.assertRaisesRegexp(ValueError, msg):
+            idx.take(np.array([1, 0, -2]), fill_value=True)
+        with tm.assertRaisesRegexp(ValueError, msg):
+            idx.take(np.array([1, 0, -5]), fill_value=True)
+
+        with tm.assertRaises(IndexError):
+            idx.take(np.array([1, -5]))
+
+    def test_take_fill_value_datetime(self):
+
+        # datetime category
+        idx = pd.DatetimeIndex(['2011-01-01', '2011-02-01', '2011-03-01'],
+                               name='xxx')
+        idx = pd.CategoricalIndex(idx)
+        result = idx.take(np.array([1, 0, -1]))
+        expected = pd.DatetimeIndex(['2011-02-01', '2011-01-01', '2011-03-01'],
+                                    name='xxx')
+        expected = pd.CategoricalIndex(expected)
+        tm.assert_index_equal(result, expected)
+
+        # fill_value
+        result = idx.take(np.array([1, 0, -1]), fill_value=True)
+        expected = pd.DatetimeIndex(['2011-02-01', '2011-01-01', 'NaT'],
+                                    name='xxx')
+        exp_cats = pd.DatetimeIndex(['2011-01-01', '2011-02-01', '2011-03-01'])
+        expected = pd.CategoricalIndex(expected, categories=exp_cats)
+        tm.assert_index_equal(result, expected)
+
+        # allow_fill=False
+        result = idx.take(np.array([1, 0, -1]), allow_fill=False,
+                          fill_value=True)
+        expected = pd.DatetimeIndex(['2011-02-01', '2011-01-01', '2011-03-01'],
+                                    name='xxx')
+        expected = pd.CategoricalIndex(expected)
+        tm.assert_index_equal(result, expected)
+
+        msg = ('When allow_fill=True and fill_value is not None, '
+               'all indices must be >= -1')
+        with tm.assertRaisesRegexp(ValueError, msg):
+            idx.take(np.array([1, 0, -2]), fill_value=True)
+        with tm.assertRaisesRegexp(ValueError, msg):
+            idx.take(np.array([1, 0, -5]), fill_value=True)
+
+        with tm.assertRaises(IndexError):
+            idx.take(np.array([1, -5]))

pandas/tests/indexes/test_multi.py

@@ -1514,6 +1514,46 @@ def test_take_preserve_name(self):
         taken = self.index.take([3, 0, 1])
         self.assertEqual(taken.names, self.index.names)
 
+    def test_take_fill_value(self):
+        # GH 12631
+        vals = [['A', 'B'],
+                [pd.Timestamp('2011-01-01'), pd.Timestamp('2011-01-02')]]
+        idx = pd.MultiIndex.from_product(vals, names=['str', 'dt'])
+
+        result = idx.take(np.array([1, 0, -1]))
+        exp_vals = [('A', pd.Timestamp('2011-01-02')),
+                    ('A', pd.Timestamp('2011-01-01')),
+                    ('B', pd.Timestamp('2011-01-02'))]
+        expected = pd.MultiIndex.from_tuples(exp_vals, names=['str', 'dt'])
+        tm.assert_index_equal(result, expected)
+
+        # fill_value
+        result = idx.take(np.array([1, 0, -1]), fill_value=True)
+        exp_vals = [('A', pd.Timestamp('2011-01-02')),
+                    ('A', pd.Timestamp('2011-01-01')),
+                    (np.nan, pd.NaT)]
+        expected = pd.MultiIndex.from_tuples(exp_vals, names=['str', 'dt'])
+        tm.assert_index_equal(result, expected)
+
+        # allow_fill=False
+        result = idx.take(np.array([1, 0, -1]), allow_fill=False,
+                          fill_value=True)
+        exp_vals = [('A', pd.Timestamp('2011-01-02')),
+                    ('A', pd.Timestamp('2011-01-01')),
+                    ('B', pd.Timestamp('2011-01-02'))]
+        expected = pd.MultiIndex.from_tuples(exp_vals, names=['str', 'dt'])
+        tm.assert_index_equal(result, expected)
+
+        msg = ('When allow_fill=True and fill_value is not None, '
+               'all indices must be >= -1')
+        with tm.assertRaisesRegexp(ValueError, msg):
+            idx.take(np.array([1, 0, -2]), fill_value=True)
+        with tm.assertRaisesRegexp(ValueError, msg):
+            idx.take(np.array([1, 0, -5]), fill_value=True)
+
+        with tm.assertRaises(IndexError):
+            idx.take(np.array([1, -5]))
+
     def test_join_level(self):
         def _check_how(other, how):
             join_index, lidx, ridx = other.join(self.index, how=how,