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REF: use public indexers in groupby.ops #31814

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Merged
merged 5 commits into from
Feb 9, 2020
Merged

REF: use public indexers in groupby.ops #31814

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d1311fd
CLN: avoid private indexer usage
jbrockmendel Feb 8, 2020
c78c9e4
Merge branch 'master' of https://github.com/pandas-dev/pandas into _g…
jbrockmendel Feb 8, 2020
9dd2110
remove commented-out
jbrockmendel Feb 8, 2020
ff89ea2
standardize on obj.iloc[:0]
jbrockmendel Feb 8, 2020
77601ec
cleanup
jbrockmendel Feb 9, 2020
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3 changes: 1 addition & 2 deletions pandas/_libs/reduction.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -309,8 +309,7 @@ cdef class SeriesGrouper(_BaseGrouper):
def __init__(self, object series, object f, object labels,
Py_ssize_t ngroups, object dummy):

# in practice we always pass either obj[:0] or the
# safer obj._get_values(slice(None, 0))
# in practice we always pass obj.iloc[:0] or equivalent
assert dummy is not None

if len(series) == 0:
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12 changes: 8 additions & 4 deletions pandas/core/groupby/ops.py
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Expand Up @@ -658,7 +658,7 @@ def _aggregate_series_fast(self, obj: Series, func):
group_index, _, ngroups = self.group_info

# avoids object / Series creation overhead
dummy = obj._get_values(slice(None, 0))
dummy = obj.iloc[:0]
indexer = get_group_index_sorter(group_index, ngroups)
obj = obj.take(indexer)
group_index = algorithms.take_nd(group_index, indexer, allow_fill=False)
Expand Down Expand Up @@ -780,7 +780,11 @@ def get_iterator(self, data: FrameOrSeries, axis: int = 0):
Generator yielding sequence of (name, subsetted object)
for each group
"""
slicer = lambda start, edge: data._slice(slice(start, edge), axis=axis)
if axis == 0:
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a more natural idiom (used in many places is)

indexer = [None] * 2
indexer[axis] = slice(start, edge)
slicer = data.iloc[indexer]

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i guess, but thats not really conducive to being a lambda

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why does this need to be a lamba?

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doesnt have to be, thats just the pattern we have now. i find iloc[:, start:end] clearer than the 3-line version

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ok

slicer = lambda start, edge: data.iloc[start:edge]
else:
slicer = lambda start, edge: data.iloc[:, start:edge]

length = len(data.axes[axis])

start = 0
Expand Down Expand Up @@ -919,7 +923,7 @@ def _chop(self, sdata, slice_obj: slice) -> NDFrame:

class SeriesSplitter(DataSplitter):
def _chop(self, sdata: Series, slice_obj: slice) -> Series:
return sdata._get_values(slice_obj)
return sdata.iloc[slice_obj]


class FrameSplitter(DataSplitter):
Expand All @@ -934,7 +938,7 @@ def _chop(self, sdata: DataFrame, slice_obj: slice) -> DataFrame:
if self.axis == 0:
return sdata.iloc[slice_obj]
else:
return sdata._slice(slice_obj, axis=1)
return sdata.iloc[:, slice_obj]


def get_splitter(data: FrameOrSeries, *args, **kwargs) -> DataSplitter:
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4 changes: 2 additions & 2 deletions pandas/tests/groupby/test_bin_groupby.py
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Expand Up @@ -11,7 +11,7 @@

def test_series_grouper():
obj = Series(np.random.randn(10))
dummy = obj[:0]
dummy = obj.iloc[:0]

labels = np.array([-1, -1, -1, 0, 0, 0, 1, 1, 1, 1], dtype=np.int64)

Expand All @@ -28,7 +28,7 @@ def test_series_grouper():
def test_series_grouper_requires_nonempty_raises():
# GH#29500
obj = Series(np.random.randn(10))
dummy = obj[:0]
dummy = obj.iloc[:0]
labels = np.array([-1, -1, -1, 0, 0, 0, 1, 1, 1, 1], dtype=np.int64)

with pytest.raises(ValueError, match="SeriesGrouper requires non-empty `series`"):
Expand Down