BUG: pandas 2.1.2 changes how copy works · Issue #55763 · pandas-dev/pandas (original) (raw)

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

class Sub(pd.DataFrame): pass

assert not isinstance(Sub().copy(), Sub)

Issue Description

Since very long ago, calling .copy() on a DataFrame subclass returned a DataFrame object. This should be changed in a major release, not a feature release, and definitely not a patch release.

Expected Behavior

The above assert statement to succeed

See also

• Probably related: BUG: Infinite recursion on inheritance and overloading __getattr__ in v2.1.0 #55120
• Downstream bug report: DataFrameView in pandas 2.1.2 changed behavior, breaking AnnData in several ways scverse/anndata#1210

Installed Versions

pandas 2.1.2 or 2.2.0.dev0+447