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fix: drop trailing separator in concat_str(..., ignore_nulls=True) for pandas-like and Dask backends - #3967
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FBruzzesi merged 11 commits intoSep 20, 2026
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FBruzzesi
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Sep 20, 2026
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FBruzzesi
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concat_str(..., ignore_nulls=True) for pandas-like and Dask backends
FBruzzesi
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Thanks for the thorough review and clean suggestions @FBruzzesi! Applied the refactoring to both pandas-like and Dask namespaces (iterative accumulation without storing intermediate series), and updated the test suite to the parameterized regression test with xfail markers for |
This was referenced Sep 22, 2026
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Description
In
concat_str(..., ignore_nulls=True), the separator between non-null values was previously derived by checking if the preceding column had a non-null value (~null_mask[:-1]). When the subsequent column was null but the preceding column was non-null, a dangling separator was still appended before the empty string, causing outputs like'x-1-'instead of'x-1'.This updates both the pandas-like and Dask implementations so that separator (i) (placed before item (i)) is included if and only if there was at least one preceding non-null value (
has_prev) AND current item (i) is non-null (~null_mask[i]).What type of PR is this? (check all applicable)
Related issues
concat_str(ignore_nulls=True)keeps the separator before a trailing null on pandas-like and Dask #3962AI assistance
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