DEPR: string indexing along index for datetimes

doc/source/whatsnew/v1.2.0.rst

@@ -195,7 +195,7 @@ Deprecations
 ~~~~~~~~~~~~
 - Deprecated parameter ``inplace`` in :meth:`MultiIndex.set_codes` and :meth:`MultiIndex.set_levels` (:issue:`35626`)
 - Deprecated parameter ``dtype`` in :~meth:`Index.copy` on method all index classes. Use the :meth:`Index.astype` method instead for changing dtype(:issue:`35853`)
--
+- Deprecated indexing :class:`DataFrame` rows with datetime-like strings ``df[string]``, use ``df.loc[string]`` instead (:issue:`????`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/indexing.py

@@ -1,4 +1,5 @@
 from typing import TYPE_CHECKING, Hashable, List, Tuple, Union
+import warnings
 
 import numpy as np
 
@@ -2154,7 +2155,15 @@ def convert_to_index_sliceable(obj: "DataFrame", key):
         # slice here via partial string indexing
         if idx._supports_partial_string_indexing:
             try:
-                return idx._get_string_slice(key)
+                res = idx._get_string_slice(key)
+                warnings.warn(
+                    "Indexing on datetimelike rows with `frame[string]` is "
+                    "deprecated and will be removed in a future version. "
+                    "Use `frame.loc[string]` instead.",
+                    FutureWarning,
+                    stacklevel=3,
+                )
+                return res
             except (KeyError, ValueError, NotImplementedError):
                 return None
 

pandas/tests/indexes/datetimes/test_partial_slicing.py

@@ -228,7 +228,9 @@ 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):
+                        # GH#???? deprecated this indexing
+                        result = df[ts_string]
                     expected = df[theslice]
                     tm.assert_frame_equal(result, expected)