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BUG: SeriesGroupby.nunique raises an IndexError on empty Series #12553 #12560

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BUG: SeriesGroupby.nunique raises an IndexError on empty Series #12553 #12560

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4 changes: 4 additions & 0 deletions pandas/core/groupby.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2843,6 +2843,10 @@ def true_and_notnull(x, *args, **kwargs):
def nunique(self, dropna=True):
""" Returns number of unique elements in the group """
ids, _, _ = self.grouper.group_info

if len(ids) == 0: # bugfix for 12553
return Series(name=self.name)

val = self.obj.get_values()

try:
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8 changes: 8 additions & 0 deletions pandas/tests/test_groupby.py
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Expand Up @@ -6465,6 +6465,14 @@ def testit(label_list, shape):
testit(label_list, shape)


def test_nunique_empty_Series():
series = Series(name='foo')
group = series.groupby(level=0)
result = group.nunique()
expected = Series(name='foo')
assert_series_equal(result, expected)
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Can you put this test inside the TestGroupBy class? Eg after test_nunique_with_object at Line 6404 (https://github.com/thanasis2028/pandas/blob/744e537c3c73ecb30a62a7707db138b7f4dafcd8/pandas/tests/test_groupby.py#L6400)



if __name__ == '__main__':
nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure', '-s'
], exit=False)