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BUG: MultiIndex.set_levels raising when setting empty level #48643

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Merged
mroeschke merged 1 commit into from
Sep 19, 2022
Merged

BUG: MultiIndex.set_levels raising when setting empty level #48643

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.6.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -175,6 +175,7 @@ Missing

MultiIndex
^^^^^^^^^^
- Bug in :class:`MultiIndex.set_levels` raising ``IndexError`` when setting empty level (:issue:`48636`)
- Bug in :meth:`MultiIndex.unique` losing extension array dtype (:issue:`48335`)
- Bug in :meth:`MultiIndex.union` losing extension array (:issue:`48498`, :issue:`48505`)
- Bug in :meth:`MultiIndex.append` not checking names for equality (:issue:`48288`)
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2 changes: 1 addition & 1 deletion pandas/core/indexes/multi.py
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Expand Up @@ -4003,7 +4003,7 @@ def _require_listlike(level, arr, arrname: str):
if level is not None and not is_list_like(level):
if not is_list_like(arr):
raise TypeError(f"{arrname} must be list-like")
if is_list_like(arr[0]):
if len(arr) > 0 and is_list_like(arr[0]):
raise TypeError(f"{arrname} must be list-like")
level = [level]
arr = [arr]
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8 changes: 8 additions & 0 deletions pandas/tests/indexes/multi/test_get_set.py
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Expand Up @@ -476,6 +476,14 @@ def test_set_levels_pos_args_deprecation():
tm.assert_index_equal(result, expected)


def test_set_empty_level():
# GH#48636
midx = MultiIndex.from_arrays([[]], names=["A"])
result = midx.set_levels(pd.DatetimeIndex([]), level=0)
expected = MultiIndex.from_arrays([pd.DatetimeIndex([])], names=["A"])
tm.assert_index_equal(result, expected)


def test_set_codes_pos_args_depreciation(idx):
# https://github.com/pandas-dev/pandas/issues/41485
msg = (
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