BUG: Add limit_area to EA ffill/bfill #56616
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rhshadrach
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Bug
Missing-data
phofl
reviewed
Dec 28, 2023
doc/source/whatsnew/v2.2.0.rst
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| @@ -313,7 +313,7 @@ Other enhancements | |||
| - :meth:`DataFrame.apply` now allows the usage of numba (via ``engine="numba"``) to JIT compile the passed function, allowing for potential speedups (:issue:`54666`) | |||
| - :meth:`ExtensionArray._explode` interface method added to allow extension type implementations of the ``explode`` method (:issue:`54833`) | |||
| - :meth:`ExtensionArray.duplicated` added to allow extension type implementations of the ``duplicated`` method (:issue:`55255`) | |||
| - :meth:`Series.ffill`, :meth:`Series.bfill`, :meth:`DataFrame.ffill`, and :meth:`DataFrame.bfill` have gained the argument ``limit_area`` (:issue:`56492`) | |||
| - :meth:`Series.ffill`, :meth:`Series.bfill`, :meth:`DataFrame.ffill`, and :meth:`DataFrame.bfill` have gained the argument ``limit_area``; 3rd part :class:`.ExtensionArray` authors need to add this argument to the method ``_pad_or_backfill`` (:issue:`56492`) | |||
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I would put this into the ExtensionArray section as well
phofl
reviewed
Dec 28, 2023
| @@ -1012,6 +1018,12 @@ def _pad_or_backfill( | |||
| DeprecationWarning, | |||
| stacklevel=find_stack_level(), | |||
| ) | |||
| if limit_area is not None: | |||
| raise NotImplementedError( | |||
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We only get here if 3rd party authors didn't implement this themselves, correct?
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Right - this is only hit when EA author overrides .fillna but not ._pad_or_backfill. Currently pandas .ffill will call the EA's .fillna in such a case, which can only be correctly done when limit_area is None.
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Friendly ping @phofl @jbrockmendel |
phofl
reviewed
Jan 3, 2024
| @@ -205,7 +210,21 @@ def _pad_or_backfill( | |||
| if copy: | |||
| npvalues = npvalues.copy() | |||
| new_mask = new_mask.copy() | |||
| elif limit_area is not None: | |||
| mask = mask.copy() | |||
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Non-blocking, but why do we need this copy here?
phofl
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Jan 3, 2024
|
thx @rhshadrach |
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…fill) (#56720) Backport PR #56616: BUG: Add limit_area to EA ffill/bfill Co-authored-by: Richard Shadrach <[email protected]>
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Opened #56729 to track the deprecation |
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limit_areapassed. #41813 (Replace xxxx with the GitHub issue number)doc/source/whatsnew/vX.X.X.rstfile if fixing a bug or adding a new feature.Follow up to #56531.
This is slightly complicated by the
EA.fillnadeprecation.EA.fillnais implemented, we raise wheneverlimit_areais not NoneEA._pad_or_backfillis implemented and does not have alimit_areaarg, we raise whenlimit_areais not NoneMy plan is to introduce a deprecation in 3.1 whenever
_pad_or_backfillgets called (regardless of whetherlimit_areaisNone) informing EA authors they need to add this argument. Assuming this is a good way to do, I'll open a tracking issue for this.For dtypes where the corresponding
maskis not used after filling (e.g.NDArrayBackedExtensionArray), this takes a shortcut by modifying mask prior to filling. Compared to implementinglimit_areaafter filling, this saves 1 or 2 copies (depending on the EA) and extra computation, at the cost of makingmaskno longer necessarily represent NA values.