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BUG: preserve object-dtype index when accessing DataFrame column / PERF: improve perf of Series fastpath constructor #42950

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Merged
merged 15 commits into from
Jan 24, 2022
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BUG: preserve object-dtype index when accessing DataFrame column / PERF: improve perf of Series fastpath constructor #42950

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64f9690
PERF: improve perf of Series fastpath constructor
jorisvandenbossche Aug 9, 2021
57659b8
pass through the fastpath arg
jorisvandenbossche Aug 9, 2021
64e7403
Merge remote-tracking branch 'upstream/master' into perf-series-const…
jorisvandenbossche Aug 11, 2021
972185f
simplify
jorisvandenbossche Aug 11, 2021
973713f
Merge remote-tracking branch 'upstream/master' into perf-series-const…
jorisvandenbossche Nov 13, 2021
a133162
Merge remote-tracking branch 'upstream/master' into perf-series-const…
jorisvandenbossche Nov 15, 2021
15e274e
Merge remote-tracking branch 'upstream/master' into perf-series-const…
jorisvandenbossche Nov 29, 2021
33fde4f
TEMP
jorisvandenbossche Nov 29, 2021
0f1ee8a
Merge remote-tracking branch 'upstream/master' into perf-series-const…
jorisvandenbossche Dec 6, 2021
22cc921
add test and whatsnew
jorisvandenbossche Dec 6, 2021
94cc2ad
Merge remote-tracking branch 'upstream/master' into perf-series-const…
jorisvandenbossche Dec 14, 2021
da90ef1
Merge remote-tracking branch 'upstream/master' into perf-series-const…
jorisvandenbossche Dec 14, 2021
2443961
Merge remote-tracking branch 'upstream/main' into perf-series-constru…
jorisvandenbossche Jan 21, 2022
0431a11
Merge remote-tracking branch 'upstream/main' into perf-series-constru…
jorisvandenbossche Jan 22, 2022
daebcf1
move whatsnew
jorisvandenbossche Jan 22, 2022
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20 changes: 12 additions & 8 deletions asv_bench/benchmarks/series_methods.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import numpy as np

from pandas import (
Index,
NaT,
Series,
date_range,
Expand All @@ -12,20 +13,23 @@


class SeriesConstructor:

params = [None, "dict"]
param_names = ["data"]

def setup(self, data):
def setup(self):
self.idx = date_range(
start=datetime(2015, 10, 26), end=datetime(2016, 1, 1), freq="50s"
)
dict_data = dict(zip(self.idx, range(len(self.idx))))
self.data = None if data is None else dict_data
self.data = dict(zip(self.idx, range(len(self.idx))))
self.array = np.array([1, 2, 3])
self.idx2 = Index(["a", "b", "c"])

def time_constructor(self, data):
def time_constructor_dict(self):
Series(data=self.data, index=self.idx)

def time_constructor_no_data(self):
Series(data=None, index=self.idx)

def time_constructor_fastpath(self):
Series(self.array, index=self.idx, name="name", fastpath=True)


class NSort:

Expand Down
40 changes: 22 additions & 18 deletions pandas/core/series.py
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Original file line number Diff line number Diff line change
Expand Up @@ -441,7 +441,11 @@ def __init__(
data = SingleArrayManager.from_array(data, index)

generic.NDFrame.__init__(self, data)
self.name = name
if fastpath:
# skips validation of the name
object.__setattr__(self, "_name", name)
else:
self.name = name
self._set_axis(0, index, fastpath=True)

def _init_dict(self, data, index=None, dtype: Dtype | None = None):
Expand Down Expand Up @@ -531,23 +535,23 @@ def _set_axis(self, axis: int, labels, fastpath: bool = False) -> None:
if not fastpath:
labels = ensure_index(labels)

if labels._is_all_dates:
deep_labels = labels
if isinstance(labels, CategoricalIndex):
deep_labels = labels.categories

if not isinstance(
deep_labels, (DatetimeIndex, PeriodIndex, TimedeltaIndex)
):
try:
labels = DatetimeIndex(labels)
# need to set here because we changed the index
if fastpath:
self._mgr.set_axis(axis, labels)
except (tslibs.OutOfBoundsDatetime, ValueError):
# labels may exceeds datetime bounds,
# or not be a DatetimeIndex
pass
if labels._is_all_dates:
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nice!

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Apparently this is being relied upon in the pytables code though ..

And looking into it further, the change I made here of course changes behaviour, as it no longer try to infer object dtype as datetime in the fastpath.

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Although that should probably be considered as a bug fix. With master:

In [1]: df = pd.DataFrame({'a': [1, 2, 3]}, index=pd.date_range("2012", periods=3).astype(object))

In [2]: df.index
Out[2]: Index([2012-01-01 00:00:00, 2012-01-02 00:00:00, 2012-01-03 00:00:00], dtype='object')

In [3]: df['a'].index
Out[3]: DatetimeIndex(['2012-01-01', '2012-01-02', '2012-01-03'], dtype='datetime64[ns]', freq=None)

where the index of the column-as-Series becomes different ..

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IIRC we deprecated this, then un-deprecated bc we didn't have good warning handling/suppression, and were going to try to re-deprecate before long

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Do you have a reference (issue/PR) for this?

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There is #36697, but that's for the non-fastpath way, I think? While here it's specifically the fastpath that I am changing (which is not used when a user creates a Series directly themselves).

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when we did that i dont remember any distinction being made between fastpath vs non-fastpath

deep_labels = labels
if isinstance(labels, CategoricalIndex):
deep_labels = labels.categories

if not isinstance(
deep_labels, (DatetimeIndex, PeriodIndex, TimedeltaIndex)
):
try:
labels = DatetimeIndex(labels)
# need to set here because we changed the index
if fastpath:
self._mgr.set_axis(axis, labels)
except (tslibs.OutOfBoundsDatetime, ValueError):
# labels may exceeds datetime bounds,
# or not be a DatetimeIndex
pass

object.__setattr__(self, "_index", labels)
if not fastpath:
Expand Down