8000 BUG: allow empty multiindex (fixes .isin regression, GH16777) by drudd · Pull Request #16782 · pandas-dev/pandas · GitHub
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BUG: allow empty multiindex (fixes .isin regression, GH16777) #16782

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Merged
merged 11 commits into from
Jul 7, 2017
Merged

BUG: allow empty multiindex (fixes .isin regression, GH16777) #16782

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17204a6
BUG: allow empty multiindex (fixes .isin regression, GH16777)
Jun 27, 2017
474ff40
BUG: allow empty multiindex (fixes .isin regression, GH16777)
Jun 27, 2017
64908e8
Replace incorrect use of self._levels with self._names
Jun 27, 2017
76967db
Requested change to whats-new
Jul 6, 2017
c84f0bc
Use names property rather than _names in MultiIndex.isin
Jul 6, 2017
f94d2b4
Revert ability to construct MultiIndex from empty arrays, ensure all …
Jul 6, 2017
fe1e043
Remove empty list checks in MultiIndex.__new__
Jul 6, 2017
b0778f0
Remove empty array check in .from_arrays, falling back to check in __…
Jul 6, 2017
e3d670a
Fix for pep8
Jul 6, 2017
39b544a
Split empty from_tuples test
Jul 6, 2017
94ac6b1
add commit number to test
jreback Jul 7, 2017
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Revert ability to construct MultiIndex from empty arrays, ensure all … 
…tests pass despite issue #16844
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@jreback
Douglas Rudd authored and jreback committed Jul 7, 2017
commit f94d2b4905d75c2a4e2328b7e90fd10d7a666fbf
14 changes: 9 additions & 5 deletions pandas/core/indexes/multi.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1083,7 +1083,9 @@ def from_arrays(cls, arrays, sortorder=None, names=None):
MultiIndex.from_product : Make a MultiIndex from cartesian product
of iterables
"""
if len(arrays) == 1:
if len(arrays) == 0:
raise ValueError('Must pass non-zero number of levels/labels')
elif len(arrays) == 1:
name = None if names is None else names[0]
return Index(arrays[0], name=name)

Expand Down Expand Up @@ -1131,10 +1133,12 @@ def from_tuples(cls, tuples, sortorder=None, names=None):
MultiIndex.from_product : Make a MultiIndex from cartesian product
of iterables
"""
if len(tuples) == 0 and names is None:
raise TypeError('Cannot infer number of levels from empty list')

if isinstance(tuples, (np.ndarray, Index)):
if len(tuples) == 0:
if names is None:
msg = 'Cannot infer number of levels from empty list'
raise TypeError(msg)
arrays = [[]]*len(names)
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this is causing a lint issue

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Fixed.

elif isinstance(tuples, (np.ndarray, Index)):
if isinstance(tuples, Index):
tuples = tuples._values

Expand Down
13 changes: 2 additions & 11 deletions pandas/tests/indexes/test_multi.py
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Expand Up @@ -766,14 +766,6 @@ def test_from_arrays_empty(self):
ValueError, "Must pass non-zero number of levels/labels"):
MultiIndex.from_arrays(arrays=[])

# 0 levels, names defined
result = MultiIndex.from_arrays(arrays=[],
names=['A', 'B'])
expected = MultiIndex(levels=[[], []],
labels=[[], []],
names=['A', 'B'])
tm.assert_index_equal(result, expected)

# 1 level
result = MultiIndex.from_arrays(arrays=[[]], names=['A'])
expected = Index([], name='A')
Expand Down Expand Up @@ -1726,9 +1718,8 @@ def test_from_tuples(self):
MultiIndex.from_tuples, [])

result = MultiIndex.from_tuples([], names=['a', 'b'])
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similary I think [(), ()] should work here

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@jorisvandenbossche jorisvandenbossche Jun 29, 2017 •
edited
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No, IMO this should not work here, as in this case you actually do pass 2 values, but empty values (not an empty container holding no values). So IMO this should raise.

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I agree with this. It should raise because you have a mismatch between the names and what you passe 8000 d. If you had NOT passed an empty list it would be ok.

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can you make the empty case a separately named test

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Done.

expected = MultiIndex(levels=[[], []],
labels=[[], []],
names=['a', 'b'])
expected = MultiIndex.from_arrays(arrays=[[], []],
names=['a', 'b'])
tm.assert_index_equal(result, expected)

idx = MultiIndex.from_tuples(((1, 2), (3, 4)), names=['a', 'b'])
Expand Down
0