DOC: update the pandas.Index.notna docstring (#20180)

Author: Donk23

pandas/core/indexes/base.py

@@ -2206,18 +2206,47 @@ def isna(self):
 
     def notna(self):
         """
-        Inverse of isna
+        Detect existing (non-missing) values.
+
+        Return a boolean same-sized object indicating if the values are not NA.
+        Non-missing values get mapped to ``True``. Characters such as empty
+        strings ``''`` or :attr:`numpy.inf` are not considered NA values
+        (unless you set ``pandas.options.mode.use_inf_as_na = True``).
+        NA values, such as None or :attr:`numpy.NaN`, get mapped to ``False``
+        values.
 
         .. versionadded:: 0.20.0
 
         Returns
         -------
-        a boolean array of whether my values are not NA
+        numpy.ndarray
+            Boolean array to indicate which entries are not NA.
 
         See also
         --------
-        notnull : alias of notna
+        Index.notnull : alias of notna
+        Index.isna: inverse of notna
         pandas.notna : top-level notna
+
+        Examples
+        --------
+        Show which entries in an Index are not NA. The result is an
+        array.
+
+        >>> idx = pd.Index([5.2, 6.0, np.NaN])
+        >>> idx
+        Float64Index([5.2, 6.0, nan], dtype='float64')
+        >>> idx.notna()
+        array([ True,  True, False])
+
+        Empty strings are not considered NA values. None is considered a NA
+        value.
+
+        >>> idx = pd.Index(['black', '', 'red', None])
+        >>> idx
+        Index(['black', '', 'red', None], dtype='object')
+        >>> idx.notna()
+        array([ True,  True,  True, False])
         """
         return ~self.isna()
     notnull = notna