DEPR: deprecate dates-with-datetime64 in _maybe_downcast_for_indexing#64871
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Discussed on today's dev call and everyone was on board. |
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Deprecate the special case in Index._maybe_downcast_for_indexing that implicitly converts sequences of datetime.date objects to DatetimeIndex when joining or indexing. This affects join, alignment, and get_indexer fallback paths where _maybe_cast_listlike_indexer does not handle the conversion. closes pandas-dev#62158 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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…-comparison * upstream/main: PERF: use lookup instead of hash_inner_join for merge with unique right keys (pandas-dev#64691) BUG : update `SeriesGroupBy.ohlc()` to honor `as_index=False` (pandas-dev#65141) PERF: Use DataFrame-level reductions in DataFrame.agg with list of funcs (pandas-dev#65031) DOC: document required external libraries in read_* I/O docstrings (pandas-dev#65143) DOC: improve MultiIndex.is_monotonic_increasing/decreasing docstrings (pandas-dev#65154) BUG: Raise ValueError for non-boolean numeric_only in DataFrame/Series reductions (GH#53098) (pandas-dev#65131) BUG: Timedelta.round() raises ZeroDivisionError when internal unit is 's' and target frequency is sub-second (pandas-dev#64836) ENH: Add replace method to Index (closes pandas-dev#19495) (pandas-dev#65099) PERF: improve StringArray.isna (pandas-dev#57733) BUG: read parquet files with older pytz (DEP: keep lower pytz minimum version) (pandas-dev#65133) DEPR: deprecate dates-with-datetime64 in _maybe_downcast_for_indexing (pandas-dev#64871) DOC: note that DataFrame.values is not writeable (pandas-dev#65142) CLN: Update groupby observed defaults (pandas-dev#65148) PERF: avoid materializing values[indexer] in Block.setitem (pandas-dev#64251) DOC: update GroupBy.sum/min/max See Also sections (pandas-dev#65144)
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Summary
Index._maybe_downcast_for_indexingthat implicitly converts sequences ofdatetime.dateobjects toDatetimeIndexwhen joining or indexingjoin, alignment, andget_indexerfallback (when_maybe_cast_listlike_indexerreturns object dtype, e.g. mixed date/Timestamp lists)_infer_matchespath (coveringequalsand the primary_maybe_cast_listlike_indexerconversion for pure date-object targets) will be handled in a separate PRcloses #62158
Test plan
Pandas4WarningDatetimeIndex.joinwith date-object Index🤖 Generated with Claude Code