Closes #5155: Bug: MultiIndex .lookup() attempts illegal dtype cast for tuple keys #5156
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
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drculhane
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Jan 15, 2026
tests/pandas/index_test.py
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| assert mask.dtype == ak.bool_ | ||
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| # Expect exactly the first row to match | ||
| assert mask.to_ndarray().tolist() == [True, False, False, False] |
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Now that I've studied this for a bit, I'd also suggest testing a lookup where the inputs are arrays. This is what I did with the above:
>>> midx.lookup(([ak.array([1,2]),ak.array(['blue','red'])]))
array([False True True False])
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Didn't mean to do this as a 'requested changes'.
drculhane
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jaketrookman
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PR Description: Improve
Index.lookupandMultiIndex.lookupsemanticsThis pull request refines type-handling, error messaging, and row/column matching
behavior for both
Index.containsandMultiIndex.lookup.It also adds a regression test ensuring that mixed-dtype tuple keys do not
trigger incorrect scalar casting.
The changes improve correctness, readability, and alignment with Pandas semantics.
Summary of Changes
1.
Index.lookupFile:
arkouda/pandas/index.pyboolean
pdarrayof lengthlen(self).TypeErrordescription to reflect that the function expects avalue convertible into an Arkouda array.
akint64).Motivation:
Clarifies semantics and avoids stale / unused imports.
2.
MultiIndex.lookupFile:
arkouda/pandas/index.pyMajor improvements to validation, dtype behavior, and membership logic:
Validation
listortuple.nlevelswith a clearValueError.Two explicit code paths
Per-level arkouda arrays (e.g. list of
pdarray/Strings)Delegated directly to
in1d(self.index, key)for vectorized matching.Scalar tuple keys (e.g.,
(1, "red"))This behavior aligns better with Pandas and eliminates subtle dtype bugs.
3. New Test: Mixed-dtype tuple lookup
File:
tests/pandas/index_test.pyAdded test
test_multiindex_lookup_tuple_mixed_dtypes:(1, "red"):"red"into numeric types.[True, False, False, False]for the provided example.Motivation:
Prevents regressions and captures a real-world bug scenario.
Why This Matters
MultiIndex.lookup.Backward Compatibility
Closes #5155: Bug: MultiIndex .lookup() attempts illegal dtype cast for tuple keys