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BUG: DataFrame.drop_duplicates method fails when a column with a list… #56958

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BUG: DataFrame.drop_duplicates method fails when a column with a list… #56958

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16 changes: 16 additions & 0 deletions pandas/core/frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6748,6 +6748,22 @@ def drop_duplicates(
DataFrame or None
DataFrame with duplicates removed or None if ``inplace=True``.

Notes
-------
To handle mutable objects such as list, convert the list column
to a tuple before using it in the subset.
Comment on lines +6753 to +6754
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This does not handle all cases. I think the note should start with something more general like:

This method requires data in the columns to be hashable.


>>> df = pd.DataFrame([
... {'number': 1, 'item_ids': [1, 2, 3]},
... {'number': 1, 'item_ids': [1, 2, 3]},
... ])

>>> df['item_ids'] = df['item_ids'].apply(tuple)
>>> df.drop_duplicates(inplace=True)
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The inplace argument should be going away (hopefully soon); it should not be used here.

>>> df['item_ids'] = df['item_ids'].apply(list)
number item_ids
0 1 [1, 2, 3]
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This line doesn't produce any output. If you want to show output, you can make it just df['items_ids'].apply(list) instead of assigning it back to the column.


See Also
--------
DataFrame.value_counts: Count unique combinations of columns.
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