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BUG: DataFrame.unstack with non-consolidated #34709

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Merged
merged 2 commits into from
Jun 14, 2020
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BUG: DataFrame.unstack with non-consolidated #34709

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07defde
BUG: DataFrame.unstack with non-consolidated
jbrockmendel Jun 11, 2020
5748801
Merge branch 'master' of https://github.com/pandas-dev/pandas into bu…
jbrockmendel Jun 13, 2020
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7 changes: 3 additions & 4 deletions pandas/core/reshape/reshape.py
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Original file line number Diff line number Diff line change
Expand Up @@ -41,8 +41,7 @@ class _Unstacker:

Parameters
----------
index : object
Pandas ``Index``
index : MultiIndex
level : int or str, default last level
Level to "unstack". Accepts a name for the level.
fill_value : scalar, optional
Expand Down Expand Up @@ -83,7 +82,7 @@ class _Unstacker:
"""

def __init__(
self, index, level=-1, constructor=None,
self, index: MultiIndex, level=-1, constructor=None,
):

if constructor is None:
Expand Down Expand Up @@ -415,7 +414,7 @@ def unstack(obj, level, fill_value=None):
level = obj.index._get_level_number(level)

if isinstance(obj, DataFrame):
if isinstance(obj.index, MultiIndex) or not obj._can_fast_transpose:
if isinstance(obj.index, MultiIndex):
return _unstack_frame(obj, level, fill_value=fill_value)
else:
return obj.T.stack(dropna=False)
Expand Down
11 changes: 11 additions & 0 deletions pandas/tests/frame/test_reshape.py
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Expand Up @@ -140,6 +140,17 @@ def test_stack_mixed_level(self):
expected = expected[["a", "b"]]
tm.assert_frame_equal(result, expected)

def test_unstack_not_consolidated(self):
# Gh#34708
df = pd.DataFrame({"x": [1, 2, np.NaN], "y": [3.0, 4, np.NaN]})
df2 = df[["x"]]
df2["y"] = df["y"]
assert len(df2._mgr.blocks) == 2

res = df2.unstack()
expected = df.unstack()
tm.assert_series_equal(res, expected)

def test_unstack_fill(self):

# GH #9746: fill_value keyword argument for Series
Expand Down