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Raise ValueError when using levels with non-unique values in MultiIndex constructor #17557

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Raise ValueError when using levels with non-unique values in MultiIndex constructor #17557

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Raise ValueError when using levels with non-unique values in MultiInd…
alanbato Sep 17, 2017
372d88b
Change % to .format string notation
alanbato Sep 17, 2017
2483ffe
Check for uniqueness with is_unique and add whatsnew
alanbato Sep 18, 2017
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5 changes: 5 additions & 0 deletions pandas/core/indexes/multi.py
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Original file line number Diff line number Diff line change
Expand Up @@ -147,6 +147,11 @@ def _verify_integrity(self, labels=None, levels=None):
" level (%d). NOTE: this index is in an"
" inconsistent state" % (i, label.max(),
len(level)))
for i, level in enumerate(levels):
if len(level) != len(set(level)):
raise ValueError("Level values must be unique: %s "
"on level %d" % ([value for value
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Can you use .format syntax instead of %? I realize that other places within this file use % formatting, but there's an ongoing effort to transition all % formatting in the pandas codebase to .format, so might as well minimize the number of changes that will need to be made.

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Of course! I do prefer .format but decided to stick with % because of the other tests. Thank you for telling me, I'll keep it in mind in future contributions :)

in level], i))

def _get_levels(self):
return self._levels
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8 changes: 8 additions & 0 deletions pandas/tests/indexes/test_multi.py
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Expand Up @@ -588,6 +588,14 @@ def test_constructor_mismatched_label_levels(self):
with tm.assert_raises_regex(ValueError, label_error):
self.index.copy().labels = [[0, 0, 0, 0], [0, 0]]

def test_constructor_non_unique_level_values(self):
# GH #17464
with tm.assert_raises_regex(ValueError, '^Level values'):
MultiIndex(levels=[[0, 1], [0, 0, 1, 1]],
labels=[[0, 0, 0, 0, 1, 1, 1, 1],
[0, 0, 1, 1, 0, 0, 1, 1]],
names=[u'idx0', u'idx1'])

def assert_multiindex_copied(self, copy, original):
# Levels should be (at least, shallow copied)
tm.assert_copy(copy.levels, original.levels)
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