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BUG: incorrect <code>cumsum</code> results for pyarrow on windows

Bug

Windowrolling, ewma, expandingrolling, ewma, expanding

WindowsWindows OSWindows OS

Status: Open.

#62477 In pandas-dev/pandas;

· MarcoGorelli opened on Sep 27, 2025

BUG: "boolean value of NA is ambiguous" when doing iloc on nullable integer series

Bug

NA - MaskedArraysRelated to pd.NA and nullable extension arraysRelated to pd.NA and nullable extension arrays

Status: Open.

#62473 In pandas-dev/pandas;

· MarcoGorelli opened on Sep 27, 2025

BUG: <code>rank</code> gives incorrect outputs on Windows with PyArrow backend

Bug

Groupby

Transformationse.g. cumsum, diff, ranke.g. cumsum, diff, rank

Upstream issueIssue related to pandas dependencyIssue related to pandas dependency

Status: Open.

#61896 In pandas-dev/pandas;

· MarcoGorelli opened on Jul 18, 2025

BUG(?): rolling sum with pyarrow types results in float64 instead of preserving integer type

Arrowpyarrow functionalitypyarrow functionality

Bug

Dtype ConversionsUnexpected or buggy dtype conversionsUnexpected or buggy dtype conversions

Windowrolling, ewma, expandingrolling, ewma, expanding

Status: Open.

#61144 In pandas-dev/pandas;

· MarcoGorelli opened on Mar 18, 2025

API: pass <code>ddof</code> down to Cythonised <code>std</code> / <code>var</code> in <code>groupby.agg</code>

API Design

Groupby

Needs DiscussionRequires discussion from core team before further actionRequires discussion from core team before further action

Reduction Operationssum, mean, min, max, etc.sum, mean, min, max, etc.

Status: Open.

#60591 In pandas-dev/pandas;

· MarcoGorelli opened on Dec 20, 2024

BUG: DatetimeIndex.is_year_start breaks for business-day frequency where <code>n</code> is greater than 1

Bug

FrequencyDateOffsetsDateOffsets

Status: Open.

#58524 In pandas-dev/pandas;

· MarcoGorelli opened on May 2, 2024

BUG: does .any(axis=1, skipna=False) follow Kleene Logic?

Bug

Reduction Operationssum, mean, min, max, etc.sum, mean, min, max, etc.

Status: Open.

#57171 In pandas-dev/pandas;

· MarcoGorelli opened on Jan 31, 2024

BUG: read_csv losing precision when reading Int64[pyarrow] data with N/A values

Arrowpyarrow functionalitypyarrow functionality

Bug

IO CSVread_csv, to_csvread_csv, to_csv

Status: Open.

#56135 In pandas-dev/pandas;

· MarcoGorelli opened on Nov 23, 2023

BUG: enlarging a DataFrame by adding an extra column with a tz-aware datetime results in object dtype

Bug

DatetimeDatetime data dtypeDatetime data dtype

Dtype ConversionsUnexpected or buggy dtype conversionsUnexpected or buggy dtype conversions

good first issue

Needs TestsUnit test(s) needed to prevent regressionsUnit test(s) needed to prevent regressions

setitem-with-expansion

Status: Open.

#55423 In pandas-dev/pandas;

· MarcoGorelli opened on Oct 6, 2023

BUG: resample('MS') may introduce trailing empty windows

Bug

DatetimeDatetime data dtypeDatetime data dtype

Status: Open.

#55284 In pandas-dev/pandas;

· MarcoGorelli opened on Sep 25, 2023

PDEP-6: special case (allow) upcasting to float when setting NaN in interval[integer] series

API Design

Status: Open.

#54790 In pandas-dev/pandas;

· MarcoGorelli opened on Aug 28, 2023

BUG: Period can be confusingly be instantiated with lowercase freq

Bug

PeriodPeriod data typePeriod data type

Status: Open.

#54105 In pandas-dev/pandas;

· MarcoGorelli opened on Jul 13, 2023