PERF: Unary methods on RangeIndex returns RangeIndex (pandas-dev#57825)

* PERF: Unary methods on RangeIndex returns RangeIndex

* Whatsnew number

Author: mroeschke

doc/source/whatsnew/v3.0.0.rst

@@ -282,6 +282,7 @@ Performance improvements
 - Performance improvement in :meth:`RangeIndex.take` returning a :class:`RangeIndex` instead of a :class:`Index` when possible. (:issue:`57445`, :issue:`57752`)
 - Performance improvement in ``DataFrameGroupBy.__len__`` and ``SeriesGroupBy.__len__`` (:issue:`57595`)
 - Performance improvement in indexing operations for string dtypes (:issue:`56997`)
+- Performance improvement in unary methods on a :class:`RangeIndex` returning a :class:`RangeIndex` instead of a :class:`Index` when possible. (:issue:`57825`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_300.bug_fixes:

pandas/core/indexes/range.py

@@ -1314,6 +1314,27 @@ def _arith_method(self, other, op):
             # test_arithmetic_explicit_conversions
             return super()._arith_method(other, op)
 
+    def __abs__(self) -> Self | Index:
+        if len(self) == 0 or self.min() >= 0:
+            return self.copy()
+        elif self.max() <= 0:
+            return -self
+        else:
+            return super().__abs__()
+
+    def __neg__(self) -> Self:
+        rng = range(-self.start, -self.stop, -self.step)
+        return self._simple_new(rng, name=self.name)
+
+    def __pos__(self) -> Self:
+        return self.copy()
+
+    def __invert__(self) -> Self:
+        if len(self) == 0:
+            return self.copy()
+        rng = range(~self.start, ~self.stop, -self.step)
+        return self._simple_new(rng, name=self.name)
+
     # error: Return type "Index" of "take" incompatible with return type
     # "RangeIndex" in supertype "Index"
     def take(  # type: ignore[override]

pandas/tests/indexes/ranges/test_range.py

@@ -763,6 +763,67 @@ def test_getitem_boolmask_wrong_length():
         ri[[True]]
 
 
+def test_pos_returns_rangeindex():
+    ri = RangeIndex(2, name="foo")
+    expected = ri.copy()
+    result = +ri
+    tm.assert_index_equal(result, expected, exact=True)
+
+
+def test_neg_returns_rangeindex():
+    ri = RangeIndex(2, name="foo")
+    result = -ri
+    expected = RangeIndex(0, -2, -1, name="foo")
+    tm.assert_index_equal(result, expected, exact=True)
+
+    ri = RangeIndex(-2, 2, name="foo")
+    result = -ri
+    expected = RangeIndex(2, -2, -1, name="foo")
+    tm.assert_index_equal(result, expected, exact=True)
+
+
+@pytest.mark.parametrize(
+    "rng, exp_rng",
+    [
+        [range(0), range(0)],
+        [range(10), range(10)],
+        [range(-2, 1, 1), range(2, -1, -1)],
+        [range(0, -10, -1), range(0, 10, 1)],
+    ],
+)
+def test_abs_returns_rangeindex(rng, exp_rng):
+    ri = RangeIndex(rng, name="foo")
+    expected = RangeIndex(exp_rng, name="foo")
+    result = abs(ri)
+    tm.assert_index_equal(result, expected, exact=True)
+
+
+def test_abs_returns_index():
+    ri = RangeIndex(-2, 2, name="foo")
+    result = abs(ri)
+    expected = Index([2, 1, 0, 1], name="foo")
+    tm.assert_index_equal(result, expected, exact=True)
+
+
+@pytest.mark.parametrize(
+    "rng",
+    [
+        range(0),
+        range(5),
+        range(0, -5, -1),
+        range(-2, 2, 1),
+        range(2, -2, -2),
+        range(0, 5, 2),
+    ],
+)
+def test_invert_returns_rangeindex(rng):
+    ri = RangeIndex(rng, name="foo")
+    result = ~ri
+    assert isinstance(result, RangeIndex)
+    expected = ~Index(list(rng), name="foo")
+    tm.assert_index_equal(result, expected, exact=False)
+
+
 @pytest.mark.parametrize(
     "rng",
     [