Avoid reindexing values assigned to a multi-index when cols_droplevel contains empty values #62404
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mroeschke
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Sep 22, 2025
doc/source/whatsnew/v3.0.0.rst
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| - Bug in :class:`DataFrame` arithmetic operations in case of unaligned MultiIndex columns (:issue:`60498`) | ||
| - Bug in :class:`DataFrame` arithmetic operations with :class:`Series` in case of unaligned MultiIndex (:issue:`61009`) | ||
| - Bug in :meth:`MultiIndex.from_tuples` causing wrong output with input of type tuples having NaN values (:issue:`60695`, :issue:`60988`) | ||
| - Bug in :meth:`DataFrame._set_item_frame_value` where column alignment logic would reindex the assigned value with an empty index, incorrectly setting all values to ``NaN``.(:issue:`61841`) |
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| - Bug in :meth:`DataFrame._set_item_frame_value` where column alignment logic would reindex the assigned value with an empty index, incorrectly setting all values to ``NaN``.(:issue:`61841`) | |
| - Bug in :meth:`DataFrame.__setitem__` where column alignment logic would reindex the assigned value with an empty index, incorrectly setting all values to ``NaN``.(:issue:`61841`) |
mroeschke
reviewed
Sep 22, 2025
doc/source/whatsnew/v3.0.0.rst
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| MultiIndex | ||
| ^^^^^^^^^^ | ||
| - :func:`DataFrame.loc` with ``axis=0`` and :class:`MultiIndex` when setting a value adds extra columns (:issue:`58116`) | ||
| - :func:`MultiIndex.get_level_values` accessing a :class:`DatetimeIndex` does not carry the frequency attribute along (:issue:`58327`, :issue:`57949`) |
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Why did all these other entries move?
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pre-commit has a check called "sort whatsnew entries alphabetically" so I assumed they need to be sorted, I'll revert the sort
mroeschke
reviewed
Sep 22, 2025
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| df2 = DataFrame([[i] for i in range(3)], columns=cols) | ||
| df3 = DataFrame([[i] for i in range(3)], columns=cols) | ||
| s1 = df1["A"].rolling(2).mean() | ||
| s2 = df2["A"].rolling(2).mean() | ||
| s3 = df3["A"].rolling(2).mean() |
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Could you just create these duplicates with .copy()?
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Sure, I'm just a bit paranoid about anything named "copy" in Python because implementing a proper deep-copy can be challenging.
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doc/source/whatsnew/vX.X.X.rstfile if fixing a bug or adding a new feature.