DEPR: row-based indexing in DataFrame.__getitem__

pandas/core/frame.py

@@ -2776,6 +2776,13 @@ def __getitem__(self, key):
         if indexer is not None:
             # either we have a slice or we have a string that can be converted
             #  to a slice for partial-string date indexing
+            if not isinstance(key, slice):
+                warnings.warn(
+                    "row-based slicing on a DataFrame is deprecated and will "
+                    "raise in a future version.  Use `df.loc[key]` instead.",
+                    FutureWarning,
+                    stacklevel=2,
+                )
             return self._slice(indexer, axis=0)
 
         # Do we have a (boolean) DataFrame?
@@ -2926,6 +2933,13 @@ def __setitem__(self, key, value):
         if indexer is not None:
             # either we have a slice or we have a string that can be converted
             #  to a slice for partial-string date indexing
+            if not isinstance(key, slice):
+                warnings.warn(
+                    "row-based slicing on a DataFrame is deprecated and will "
+                    "raise in a future version.  Use `df.loc[key]` instead.",
+                    FutureWarning,
+                    stacklevel=2,
+                )
             return self._setitem_slice(indexer, value)
 
         if isinstance(key, DataFrame) or getattr(key, "ndim", None) == 2:

pandas/core/indexing.py

@@ -1,4 +1,4 @@
-from typing import Hashable, List, Tuple, Union
+from typing import TYPE_CHECKING, Hashable, List, Tuple, Union
 
 import numpy as np
 
@@ -29,6 +29,10 @@
 )
 from pandas.core.indexes.api import Index
 
+if TYPE_CHECKING:
+    from pandas import DataFrame
+
+
 # "null slice"
 _NS = slice(None, None)
 
@@ -2167,7 +2171,7 @@ def _tuplify(ndim: int, loc: Hashable) -> Tuple[Union[Hashable, slice], ...]:
     return tuple(_tup)
 
 
-def convert_to_index_sliceable(obj, key):
+def convert_to_index_sliceable(obj: "DataFrame", key):
     """
     If we are index sliceable, then return my slicer, otherwise return None.
     """

pandas/tests/indexes/datetimes/test_partial_slicing.py

@@ -309,7 +309,8 @@ def test_partial_slicing_dataframe(self):
                     tm.assert_series_equal(result, expected)
 
                     # Frame should return slice as well
-                    result = df[ts_string]
+                    with tm.assert_produces_warning(FutureWarning):
+                        result = df[ts_string]
                     expected = df[theslice]
                     tm.assert_frame_equal(result, expected)
 

pandas/tests/series/indexing/test_datetime.py

@@ -641,7 +641,9 @@ def test_indexing():
     expected.name = "A"
 
     df = DataFrame(dict(A=ts))
-    result = df["2001"]["A"]
+    with tm.assert_produces_warning(FutureWarning):
+        ser = df["2001"]
+    result = ser["A"]
     tm.assert_series_equal(expected, result)
 
     # setting
@@ -651,7 +653,9 @@ def test_indexing():
 
     df.loc["2001", "A"] = 1
 
-    result = df["2001"]["A"]
+    with tm.assert_produces_warning(FutureWarning):
+        ser = df["2001"]
+    result = ser["A"]
     tm.assert_series_equal(expected, result)
 
     # GH3546 (not including times on the last day)