Backport PR on Branch 1.5.x (REV: revert deprecation of Series.__geti…

…tem__ slicing with IntegerIndex) (#50694)

* REV: revert deprecation of Series.__getitem__ slicing with IntegerIndex (#50283)

(cherry picked from commit 1613f26)

* Avoid unrelated changes

* Fix

Co-authored-by: jbrockmendel <jbrockmendel@gmail.com>

doc/source/whatsnew/v1.5.3.rst

@@ -46,7 +46,7 @@ Other
     you may see a ``sqlalchemy.exc.RemovedIn20Warning``. These warnings can be safely ignored for the SQLAlchemy 1.4.x releases
     as pandas works toward compatibility with SQLAlchemy 2.0.
 
--
+- Reverted deprecation (:issue:`45324`) of behavior of :meth:`Series.__getitem__` and :meth:`Series.__setitem__` slicing with an integer :class:`Index`; this will remain positional (:issue:`49612`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/indexes/base.py

@@ -123,7 +123,6 @@
     ABCDatetimeIndex,
     ABCMultiIndex,
     ABCPeriodIndex,
-    ABCRangeIndex,
     ABCSeries,
     ABCTimedeltaIndex,
 )
@@ -4213,7 +4212,7 @@ def _validate_positional_slice(self, key: slice) -> None:
         self._validate_indexer("positional", key.stop, "iloc")
         self._validate_indexer("positional", key.step, "iloc")
 
-    def _convert_slice_indexer(self, key: slice, kind: str_t, is_frame: bool = False):
+    def _convert_slice_indexer(self, key: slice, kind: str_t):
         """
         Convert a slice indexer.
 
@@ -4224,9 +4223,6 @@ def _convert_slice_indexer(self, key: slice, kind: str_t, is_frame: bool = False
         ----------
         key : label of the slice bound
         kind : {'loc', 'getitem'}
-        is_frame : bool, default False
-            Whether this is a slice called on DataFrame.__getitem__
-            as opposed to Series.__getitem__
         """
         assert kind in ["loc", "getitem"], kind
 
@@ -4248,46 +4244,7 @@ def is_int(v):
         is_positional = is_index_slice and ints_are_positional
 
         if kind == "getitem":
-            """
-            called from the getitem slicers, validate that we are in fact
-            integers
-            """
-            if self.is_integer():
-                if is_frame:
-                    # unambiguously positional, no deprecation
-                    pass
-                elif start is None and stop is None:
-                    # label-based vs positional is irrelevant
-                    pass
-                elif isinstance(self, ABCRangeIndex) and self._range == range(
-                    len(self)
-                ):
-                    # In this case there is no difference between label-based
-                    #  and positional, so nothing will change.
-                    pass
-                elif (
-                    self.dtype.kind in ["i", "u"]
-                    and self._is_strictly_monotonic_increasing
-                    and len(self) > 0
-                    and self[0] == 0
-                    and self[-1] == len(self) - 1
-                ):
-                    # We are range-like, e.g. created with Index(np.arange(N))
-                    pass
-                elif not is_index_slice:
-                    # we're going to raise, so don't bother warning, e.g.
-                    #  test_integer_positional_indexing
-                    pass
-                else:
-                    warnings.warn(
-                        "The behavior of `series[i:j]` with an integer-dtype index "
-                        "is deprecated. In a future version, this will be treated "
-                        "as *label-based* indexing, consistent with e.g. `series[i]` "
-                        "lookups. To retain the old behavior, use `series.iloc[i:j]`. "
-                        "To get the future behavior, use `series.loc[i:j]`.",
-                        FutureWarning,
-                        stacklevel=find_stack_level(),
-                    )
+            # called from the getitem slicers, validate that we are in fact integers
             if self.is_integer() or is_index_slice:
                 # Note: these checks are redundant if we know is_index_slice
                 self._validate_indexer("slice", key.start, "getitem")

pandas/core/indexes/interval.py

@@ -779,7 +779,7 @@ def _index_as_unique(self) -> bool:
         "cannot handle overlapping indices; use IntervalIndex.get_indexer_non_unique"
     )
 
-    def _convert_slice_indexer(self, key: slice, kind: str, is_frame: bool = False):
+    def _convert_slice_indexer(self, key: slice, kind: str):
         if not (key.step is None or key.step == 1):
             # GH#31658 if label-based, we require step == 1,
             #  if positional, we disallow float start/stop
@@ -791,7 +791,7 @@ def _convert_slice_indexer(self, key: slice, kind: str, is_frame: bool = False):
                     # i.e. this cannot be interpreted as a positional slice
                     raise ValueError(msg)
 
-        return super()._convert_slice_indexer(key, kind, is_frame=is_frame)
+        return super()._convert_slice_indexer(key, kind)
 
     @cache_readonly
     def _should_fallback_to_positional(self) -> bool:

pandas/core/indexes/numeric.py

@@ -219,7 +219,7 @@ def _should_fallback_to_positional(self) -> bool:
         return False
 
     @doc(Index._convert_slice_indexer)
-    def _convert_slice_indexer(self, key: slice, kind: str, is_frame: bool = False):
+    def _convert_slice_indexer(self, key: slice, kind: str):
         # TODO(2.0): once #45324 deprecation is enforced we should be able
         #  to simplify this.
         if is_float_dtype(self.dtype):
@@ -231,7 +231,7 @@ def _convert_slice_indexer(self, key: slice, kind: str, is_frame: bool = False):
             # translate to locations
             return self.slice_indexer(key.start, key.stop, key.step)
 
-        return super()._convert_slice_indexer(key, kind=kind, is_frame=is_frame)
+        return super()._convert_slice_indexer(key, kind=kind)
 
     @doc(Index._maybe_cast_slice_bound)
     def _maybe_cast_slice_bound(self, label, side: str, kind=lib.no_default):

pandas/core/indexing.py

@@ -2491,7 +2491,7 @@ def convert_to_index_sliceable(obj: DataFrame, key):
     """
     idx = obj.index
     if isinstance(key, slice):
-        return idx._convert_slice_indexer(key, kind="getitem", is_frame=True)
+        return idx._convert_slice_indexer(key, kind="getitem")
 
     elif isinstance(key, str):
 

pandas/tests/extension/base/getitem.py

@@ -313,8 +313,7 @@ def test_get(self, data):
         expected = s.iloc[[2, 3]]
         self.assert_series_equal(result, expected)
 
-        with tm.assert_produces_warning(FutureWarning, match="label-based"):
-            result = s.get(slice(2))
+        result = s.get(slice(2))
         expected = s.iloc[[0, 1]]
         self.assert_series_equal(result, expected)
 

pandas/tests/indexing/test_floats.py

@@ -340,8 +340,7 @@ def test_integer_positional_indexing(self, idx):
         """
         s = Series(range(2, 6), index=range(2, 6))
 
-        with tm.assert_produces_warning(FutureWarning, match="label-based"):
-            result = s[2:4]
+        result = s[2:4]
         expected = s.iloc[2:4]
         tm.assert_series_equal(result, expected)
 

pandas/tests/series/indexing/test_get.py

@@ -167,8 +167,7 @@ def test_get_with_ea(arr):
     expected = ser.iloc[[2, 3]]
     tm.assert_series_equal(result, expected)
 
-    with tm.assert_produces_warning(FutureWarning, match="label-based"):
-        result = ser.get(slice(2))
+    result = ser.get(slice(2))
     expected = ser.iloc[[0, 1]]
     tm.assert_series_equal(result, expected)
 

pandas/tests/series/indexing/test_getitem.py

@@ -338,8 +338,7 @@ def test_getitem_slice_bug(self):
     def test_getitem_slice_integers(self):
         ser = Series(np.random.randn(8), index=[2, 4, 6, 8, 10, 12, 14, 16])
 
-        with tm.assert_produces_warning(FutureWarning, match="label-based"):
-            result = ser[:4]
+        result = ser[:4]
         expected = Series(ser.values[:4], index=[2, 4, 6, 8])
         tm.assert_series_equal(result, expected)
 

pandas/tests/series/indexing/test_setitem.py

@@ -220,15 +220,9 @@ def test_setitem_slice(self):
     def test_setitem_slice_integers(self):
         ser = Series(np.random.randn(8), index=[2, 4, 6, 8, 10, 12, 14, 16])
 
-        msg = r"In a future version, this will be treated as \*label-based\* indexing"
-        with tm.assert_produces_warning(FutureWarning, match=msg):
-            ser[:4] = 0
-        with tm.assert_produces_warning(
-            FutureWarning, match=msg, check_stacklevel=False
-        ):
-            assert (ser[:4] == 0).all()
-        with tm.assert_produces_warning(FutureWarning, match=msg):
-            assert not (ser[4:] == 0).any()
+        ser[:4] = 0
+        assert (ser[:4] == 0).all()
+        assert not (ser[4:] == 0).any()
 
     def test_setitem_slicestep(self):
         # caught this bug when writing tests