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API: setitem-with-expansion casting

API - ConsistencyInternal Consistency of API/BehaviorInternal Consistency of API/Behavior

setitem-with-expansion

Status: Open.

#62369 In pandas-dev/pandas;

· jbrockmendel opened on Sep 17, 2025

BUG: loc __setitem__ has incorrect behavior when assigned a DataFrame and new columns and duplicated columns are added.

Bug

IndexingRelated to indexing on series/frames, not to indexes themselvesRelated to indexing on series/frames, not to indexes themselves

Needs TriageIssue that has not been reviewed by a pandas team memberIssue that has not been reviewed by a pandas team member

setitem-with-expansion

Status: Open.

#58317 In pandas-dev/pandas;

· sfc-gh-vbudati opened on Apr 18, 2024

BUG: loc __setitem__ uses empty byte values for column unknowns when both rows and columns are added/DataFrame is enlarged

Bug

Needs TriageIssue that has not been reviewed by a pandas team memberIssue that has not been reviewed by a pandas team member

setitem-with-expansion

Status: Open.

#58316 In pandas-dev/pandas;

· sfc-gh-vbudati opened on Apr 18, 2024

BUG: upcasting when assigning to an enlarged series does not produce a FutureWarning

Bug

Needs TriageIssue that has not been reviewed by a pandas team memberIssue that has not been reviewed by a pandas team member

setitem-with-expansion

Status: Open.

#57853 In pandas-dev/pandas;

· arnaudlegout opened on Mar 15, 2024

BUG: Unexpected behaviour when inserting timestamps into Series

Bug

IndexingRelated to indexing on series/frames, not to indexes themselvesRelated to indexing on series/frames, not to indexes themselves

Needs TriageIssue that has not been reviewed by a pandas team memberIssue that has not been reviewed by a pandas team member

setitem-with-expansion

Status: Open.

#57596 In pandas-dev/pandas;

· KowalMar opened on Feb 24, 2024

BUG: incompatible dtype when creating bool column with df.at

Bug

Needs TriageIssue that has not been reviewed by a pandas team memberIssue that has not been reviewed by a pandas team member

setitem-with-expansion

Status: Open.

#56600 In pandas-dev/pandas;

· charizard-knows opened on Dec 22, 2023

BUG: expanding dataframe row-wise with single-element-list is no-op, but two-element-list copies

Bug

setitem-with-expansion

Status: Open.

#56203 In pandas-dev/pandas;

· MarcoGorelli opened on Nov 27, 2023

BUG: time deltas are always inferred as pd.Timedelta

setitem-with-expansion

TimedeltaTimedelta data typeTimedelta data type

Status: Open.

#56010 In pandas-dev/pandas;

· phofl opened on Nov 16, 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: Setting a pyarrow scalar value with the same type that expands the series changes the dtype into object

Arrowpyarrow functionalitypyarrow functionality

Bug

IndexingRelated to indexing on series/frames, not to indexes themselvesRelated to indexing on series/frames, not to indexes themselves

setitem-with-expansion

Status: Open.

#52235 In pandas-dev/pandas;

· char101 opened on Mar 27, 2023

BUG: Cannot use .loc to set a ndarray as the value of an empty dataframe

Bug

IndexingRelated to indexing on series/frames, not to indexes themselvesRelated to indexing on series/frames, not to indexes themselves

setitem-with-expansion

Status: Open.

#49972 In pandas-dev/pandas;

· LouisLU9911 opened on Nov 30, 2022

BUG: DataFrame.at allows adding new rows to a DataFrame

DeprecateFunctionality to remove in pandasFunctionality to remove in pandas

IndexingRelated to indexing on series/frames, not to indexes themselvesRelated to indexing on series/frames, not to indexes themselves

setitem-with-expansion

Status: Open.

#48323 In pandas-dev/pandas;

· rhshadrach opened on Aug 31, 2022