BUG: Raise clear error for duplicate id_vars in melt (GH61475) #61484
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| # GH61475 - prevent AttributeError when duplicate column | ||
| if not hasattr(id_data, "dtype"): | ||
| raise Exception(f"{col} is a duplicate column header") |
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- This should check
if not frame.columns.is_uniqueat the beginning of the function. - A
ValueErroris more appropriate here
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Thanks for the feedback! I've moved the check for not frame.columns.is_unique to the beginning of the function and updated the exception type to ValueError as suggested.
A quick clarification question: currently melt allows duplicate column names in 'value_vars', as seen in the test test_melt_with_duplicate_columns.With this change, are we treating any duplicate columns in the input DataFrame as a ValueError? Not just when the duplicates appear in id_vars?
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Ah good point. I guess this specifically when id_vars is not empty we'll want to raise if not frame.columns.is_unique
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Thanks! Just to make sure I understand:
You're saying that we should only raise an error in duplicate column names if the duplicate is in id_vars, correct? Essentially if the duplicates are in value_vars then, we can let the melt function work as is, as long as no errors are occuring?
mroeschke
added
Reshaping
doc/source/whatsnew/vX.X.X.rstfile if fixing a bug or adding a new feature.