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CLN: improve is_unique check in Index.intersection #38154

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Merged
merged 5 commits into from
Dec 2, 2020
Merged

CLN: improve is_unique check in Index.intersection #38154

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79d6a50
Improve is_unqiue check
phofl Nov 29, 2020
53e69f7
Improve assert
phofl Nov 29, 2020
6ec04c1
Remove index
phofl Nov 29, 2020
cd1acca
Add unique check to Index.unique
phofl Nov 29, 2020
aba0f2a
Add shallow copy
phofl Nov 29, 2020
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8 changes: 6 additions & 2 deletions pandas/core/indexes/base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2858,13 +2858,17 @@ def _intersection(self, other, sort=False):
indexer = algos.unique1d(Index(rvals).get_indexer_non_unique(lvals)[0])
indexer = indexer[indexer != -1]

result = other.take(indexer).unique()._values
result = other.take(indexer)
if not result.is_unique:
result = result.unique()._values
else:
result = result._values
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im surprised this makes a difference. Index.unique should already be doing this check internally i guess

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@jreback suggested to check for uniqueness before calling unique() to save a bit of time.

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actually @jbrockmendel makes a very good point here. Let's repurpose this PR to actually do a uniquess check internal to unique (of course this may only make sense for > 1000 elements or something).


if sort is None:
result = algos.safe_sort(result)

# Intersection has to be unique
assert algos.unique(result).shape == result.shape
assert Index(result).is_unique

return result

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