CLN: remove broken Index.__inv__ from Python 3, add Index.__invert__

closes #22335

Author: toobaz

doc/source/whatsnew/v0.24.0.txt

@@ -614,6 +614,8 @@ Indexing
 - Fixed ``DataFrame[np.nan]`` when columns are non-unique (:issue:`21428`)
 - Bug when indexing :class:`DatetimeIndex` with nanosecond resolution dates and timezones (:issue:`11679`)
 - Bug where indexing with a Numpy array containing negative values would mutate the indexer (:issue:`21867`)
+- Method :meth:`Index.__inv__` was suppressed, as it provided the same functionality as :meth:`Index.__neg__` rather than what its name suggested; :meth:`Index.__invert__` was added instead, and the ``~`` operator now works (analogously as for :class:`Series`) (:issue:`21688`)
+-
 
 Missing
 ^^^^^^^
@@ -688,4 +690,3 @@ Other
 - :meth: `~pandas.io.formats.style.Styler.background_gradient` now also supports tablewise application (in addition to rowwise and columnwise) with ``axis=None`` (:issue:`15204`)
 -
 -
--

pandas/core/indexes/base.py

@@ -4689,7 +4689,7 @@ def _add_numeric_methods_disabled(cls):
         cls.__neg__ = make_invalid_op('__neg__')
         cls.__pos__ = make_invalid_op('__pos__')
         cls.__abs__ = make_invalid_op('__abs__')
-        cls.__inv__ = make_invalid_op('__inv__')
+        cls.__invert__ = make_invalid_op('__invert__')
 
     def _maybe_update_attributes(self, attrs):
         """ Update Index attributes (e.g. freq) depending on op """
@@ -4786,7 +4786,7 @@ def _evaluate_numeric_unary(self):
         cls.__neg__ = _make_evaluate_unary(operator.neg, '__neg__')
         cls.__pos__ = _make_evaluate_unary(operator.pos, '__pos__')
         cls.__abs__ = _make_evaluate_unary(np.abs, '__abs__')
-        cls.__inv__ = _make_evaluate_unary(lambda x: -x, '__inv__')
+        cls.__invert__ = _make_evaluate_unary(np.invert, '__invert__')
 
     @classmethod
     def _add_numeric_methods(cls):

pandas/tests/test_arithmetic.py

@@ -15,7 +15,7 @@
 from pandas._libs.tslibs import IncompatibleFrequency
 from pandas import (
     timedelta_range,
-    Timedelta, Timestamp, NaT, Series, TimedeltaIndex, DatetimeIndex,
+    Timedelta, Timestamp, NaT, Series, Index, TimedeltaIndex, DatetimeIndex,
     DataFrame)
 
 
@@ -73,6 +73,41 @@ def box_df_fail(request):
     return request.param
 
 
+# ------------------------------------------------------------------
+# Numeric types Arithmetic Operations
+
+class TestNumericOps(object):
+
+    @pytest.mark.parametrize('opname', ['neg', 'pos', 'abs', 'inv', 'invert'])
+    @pytest.mark.parametrize('dtype', [int, float, object])
+    def test_numeric_unary_ops(self, box, dtype, opname):
+        # GH 22335
+        data = [-2, 0, 4, 5]
+        obj = box(data, dtype=dtype)
+
+        def call_method():
+            return getattr(obj, '__{}__'.format(opname))()
+
+        if opname == 'inv':
+            # GH 22335 - 'inv' was wrong and was removed
+            pytest.raises(AttributeError, call_method)
+            return
+        if opname == 'invert' and dtype is float:
+            # inversion of floats is undefined
+            pytest.raises(TypeError, call_method)
+            return
+        if dtype in (object, bool) and isinstance(obj, Index):
+            # GH 16873 - numeric operations on 'object' dtype might be removed
+            # from NDFrames as well
+            pytest.raises(TypeError, call_method)
+            return
+
+        result = call_method()
+        library_op = getattr(operator, opname)
+        expected = box([library_op(i) for i in data], dtype=dtype)
+        tm.assert_equal(result, expected)
+
+
 # ------------------------------------------------------------------
 # Timedelta64[ns] dtype Comparisons