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ENH: add ignore index logic for df.isin() function

Enhancement

isinisin methodisin method

ReshapingConcat, Merge/Join, Stack/Unstack, ExplodeConcat, Merge/Join, Stack/Unstack, Explode

Status: Open (in progress).

pandas-dev/pandasnumber 62620

#62620 In pandas-dev/pandas;

· saakshimore opened on Oct 7, 2025

BUG: Implicit conversion to float64 with isin()

Bug

Dtype ConversionsUnexpected or buggy dtype conversionsUnexpected or buggy dtype conversions

isinisin methodisin method

Status: Open.

#61676 In pandas-dev/pandas;

· pbrochart opened on Jun 18, 2025

BUG: isin check with numpy array works incorrectly when using UInt64 dtype

Bug

isinisin methodisin method

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

Status: Open.

#59609 In pandas-dev/pandas;

· qltwis opened on Aug 26, 2024

BUG: <code>isin</code> propagates nulls for DataFrame but not Series

Bug

isinisin methodisin method

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

Status: Open.

#46326 In pandas-dev/pandas;

· brandon-b-miller opened on Mar 11, 2022

ENH: Behaviour Series.isin with dataframe comparison is confusing [for discussion]

Error ReportingIncorrect or improved errors from pandasIncorrect or improved errors from pandas

isinisin methodisin method

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

Status: Open.

#43460 In pandas-dev/pandas;

· erfannariman opened on Sep 8, 2021

ENH: consider using sets and not maps for isin, unique and duplicated

duplicatedduplicated, drop_duplicatesduplicated, drop_duplicates

Enhancement

isinisin methodisin method

PerformanceMemory or execution speed performanceMemory or execution speed performance

Status: Open.

#39799 In pandas-dev/pandas;

· realead opened on Feb 13, 2021

different behaviour of df.isin() in 1.0.5/1.1.0, when df contains None

Bug

isinisin methodisin method

Missing-datanp.nan, pd.NaT, pd.NA, dropna, isnull, interpolatenp.nan, pd.NaT, pd.NA, dropna, isnull, interpolate

RegressionFunctionality that used to work in a prior pandas versionFunctionality that used to work in a prior pandas version

Status: Open.

#35565 In pandas-dev/pandas;

· johny-b opened on Aug 5, 2020

incosistencies in dataframe.dtype.isin() - I am getting inconsistent with different runs on same code.

Bug

hashinghash_pandas_objecthash_pandas_object

isinisin methodisin method

Upstream issueIssue related to pandas dependencyIssue related to pandas dependency

Status: Open.

#32443 In pandas-dev/pandas;

· maleknia opened on Mar 4, 2020

How should isin behave with pd.NA?

Bug

isinisin methodisin method

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

Status: Open.

#31990 In pandas-dev/pandas;

· dsaxton opened on Feb 15, 2020

pd.MultiIndex.isin doesn't validate input correctly

Bug

Error ReportingIncorrect or improved errors from pandasIncorrect or improved errors from pandas

isinisin methodisin method

MultiIndex

Status: Open.

#26622 In pandas-dev/pandas;

· telamonian opened on Jun 2, 2019

pandas.Series.isin() is slow on large sets due to conversion of set to list

isinisin methodisin method

PerformanceMemory or execution speed performanceMemory or execution speed performance

Status: Open.

#25507 In pandas-dev/pandas;

· amerberg opened on Mar 1, 2019

MultiIndex.isin should handle input dims better

Enhancement

Error ReportingIncorrect or improved errors from pandasIncorrect or improved errors from pandas

isinisin methodisin method

MultiIndex

Status: Open.

#20252 In pandas-dev/pandas;

· TomAugspurger opened on Mar 10, 2018