ENH: .isnull and .notnull have been added as methods to Index to make this more consistent with the Series API

Author: jreback

doc/source/api.rst

@@ -1356,8 +1356,16 @@ Modifying and Computations
    Index.unique
    Index.nunique
    Index.value_counts
+
+Missing Values
+~~~~~~~~~~~~~~
+.. autosummary::
+   :toctree: generated/
+
    Index.fillna
    Index.dropna
+   Index.isnull
+   Index.notnull
 
 Conversion
 ~~~~~~~~~~

doc/source/whatsnew/v0.20.0.txt

@@ -125,7 +125,7 @@ Other enhancements
 
 - ``pd.read_excel`` now preserves sheet order when using ``sheetname=None`` (:issue:`9930`)
 - Multiple offset aliases with decimal points are now supported (e.g. '0.5min' is parsed as '30s') (:issue:`8419`)
-
+- ``.isnull()`` and ``.notnull()`` have been added to ``Index`` object to make them more consistent with the ``Series`` API (:issue:`15300`)
 - ``pd.read_gbq`` method now allows query configuration preferences (:issue:`14742`)
 
 - New ``UnsortedIndexError`` (subclass of ``KeyError``) raised when indexing/slicing into an

pandas/indexes/base.py

@@ -1662,6 +1662,38 @@ def hasnans(self):
         else:
             return False
 
+    def isnull(self):
+        """
+        Detect missing values
+
+        .. versionadded:: 0.20.0
+
+        Returns
+        -------
+        a boolean array of whether my values are null
+
+        See also
+        --------
+        pandas.isnull : pandas version
+        """
+        return self._isnan
+
+    def notnull(self):
+        """
+        Reverse of isnull
+
+        .. versionadded:: 0.20.0
+
+        Returns
+        -------
+        a boolean array of whether my values are not null
+
+        See also
+        --------
+        pandas.notnull : pandas version
+        """
+        return ~self.isnull()
+
     def putmask(self, mask, value):
         """
         return a new Index of the values set with the mask

pandas/tests/indexes/common.py

@@ -879,3 +879,25 @@ def test_fillna(self):
                 expected[1] = True
                 self.assert_numpy_array_equal(idx._isnan, expected)
                 self.assertTrue(idx.hasnans)
+
+    def test_nulls(self):
+        # this is really a smoke test for the methods
+        # as these are adequantely tested for function elsewhere
+
+        for name, index in self.indices.items():
+            if len(index) == 0:
+                self.assert_numpy_array_equal(index.isnull(), np.array([], dtype=bool))
+            elif isinstance(index, MultiIndex):
+                idx = index.copy()
+                msg = "isnull is not defined for MultiIndex"
+                with self.assertRaisesRegexp(NotImplementedError, msg):
+                    idx.isnull()
+            else:
+
+                if not index.hasnans:
+                    self.assert_numpy_array_equal(index.isnull(), np.zeros(len(index), dtype=bool))
+                    self.assert_numpy_array_equal(index.notnull(), np.ones(len(index), dtype=bool))
+                else:
+                    result = isnull(index)
+                    self.assert_numpy_array_equal(index.isnull(), result)
+                    self.assert_numpy_array_equal(index.notnull(), ~result)