Preserve column names in empty Dataframe #61143
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…if nrows == 0' to return Cls(columns=columns) in core/frame.py. - Added test to verify column preservation.
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rhshadrach
requested changes
Mar 19, 2025
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Thanks for the PR! When making a PR, follow these steps here:
https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#making-a-pull-request
namely step 4.
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| def test_empty_df_preserve_col(): | ||
| rows = [] | ||
| df = pd.DataFrame.from_records(iter(rows), columns=['col_1', 'Col_2'], nrows=0) | ||
| assert list(df.columns)==['col_1', 'Col_2'] | ||
| assert len(df) == 0 |
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Can you follow the dev docs here: https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests
Namely, search the current tests for from_records and that should give a good indication of where to place this test.
rhshadrach
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Description
Updates pandas/core/frame.py to preserve column names in empty DataFrames when nrows == 0. Changed from return Cls() to return Cls(columns=columns).
Changes Made
Testing