BUG: Sorting fails in specific cases with pandas==2.1.1

[nancy-pm]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd

# Example data
data = {'A': [3, 1, 2], 'B': ['x', 'y', 'z']}
df = pd.DataFrame(data)

# Sorting operation
sorted_df = df.sort_values(by='A')
print(sorted_df)

Issue Description

I’ve encountered an issue where sorting operations fail under specific conditions when using pandas==2.1.1. This behavior does not occur in pandas==1.5.3, which suggests it might be a regression or a bug introduced in newer versions.

Expected Behavior

Additional Context:

This issue does not occur in pandas==1.5.3.
I’ve tested this in multiple environments and confirmed the behavior.
If more details are needed, I can provide additional examples or data.
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Installed Versions

Environment:

Python version: [e.g., 3.9.12]
Pandas version: 2.1.1
Operating System: [ Windows 10]

[nancy-pm]

Currently, the output appears correct, but I’d like to ensure there are no edge cases or hidden issues.

Environment:

Python version: [e.g., 3.9.12]
Pandas version: 2.1.1
Operating System: [e.g., Windows 10, macOS, Linux]
Additional Context:

This request is prompted by reports of sorting-related issues in other methods (e.g., sort_values) in pandas==2.1.1.
A thorough review of sort_index would help ensure its reliability across all use cases.
If needed, I can provide additional test cases or data.

[Liam3851]

Note that pandas 2.1.1 is not the latest release, that is pandas 2.2.3.

If you have an example of code that does not work please submit it for reproduction, as it is very difficult to diagnose a bug where, as you state, the output currently appears correct.

[rhshadrach]

@nancy-pm - can you post the output you believe is incorrect.

[Liam3851]

FWIW there was a known sorting regression in pandas 2.1.1 that was fixed in 2.1.2: #55379.

[rhshadrach]

Without information this issue is not actionable. Closing.