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REGR: NotImplementedError: Prefix not defined when slicing offset with loc #47547

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Merged
merged 14 commits into from
Aug 23, 2022
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REGR: NotImplementedError: Prefix not defined when slicing offset with loc #47547

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5fc5b04
fix regression
CloseChoice Jun 29, 2022
92c499e
add whatsnew entry
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e92c3e2
run pre-commit
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7086415
remove todo in code
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6572ad2
fix quotes
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62abb79
Merge branch 'main' of github.com:pandas-dev/pandas into 2022-06-29-F…
CloseChoice Jul 11, 2022
d9fa426
update tests
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fb11c66
update test
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b2ae03d
Merge branch 'main' of github.com:pandas-dev/pandas into 2022-06-29-F…
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07af101
Merge remote-tracking branch 'upstream/main' into 2022-06-29-FIX-46671
jorisvandenbossche Aug 20, 2022
54bd158
update test_getitem
CloseChoice Aug 21, 2022
d6a219b
Merge branch 'main' into 2022-06-29-FIX-46671
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d9c85e5
Update doc/source/whatsnew/v1.4.4.rst
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Merge branch 'main' into 2022-06-29-FIX-46671
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.4.4.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ Fixed regressions
- Fixed regression in :meth:`DataFrame.loc` not updating the cache correctly after values were set (:issue:`47867`)
- Fixed regression in :meth:`DataFrame.loc` not aligning index in some cases when setting a :class:`DataFrame` (:issue:`47578`)
- Fixed regression in :meth:`DataFrame.loc` setting a length-1 array like value to a single value in the DataFrame (:issue:`46268`)
- Fixed regression when slicing with :meth:`DataFrame.loc` with :class:`DateOffset`-index (:issue:`46671`)
- Fixed regression in setting ``None`` or non-string value into a ``string``-dtype Series using a mask (:issue:`47628`)
- Fixed regression using custom Index subclasses (for example, used in xarray) with :meth:`~DataFrame.reset_index` or :meth:`Index.insert` (:issue:`47071`)
- Fixed regression in :meth:`DatetimeIndex.intersection` when the :class:`DatetimeIndex` has dates crossing daylight savings time (:issue:`46702`)
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7 changes: 6 additions & 1 deletion pandas/core/indexes/datetimelike.py
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Expand Up @@ -223,7 +223,12 @@ def _parsed_string_to_bounds(self, reso: Resolution, parsed):

def _parse_with_reso(self, label: str):
# overridden by TimedeltaIndex
parsed, reso_str = parsing.parse_time_string(label, self.freq)
try:
if self.freq is None or hasattr(self.freq, "rule_code"):
freq = self.freq
except NotImplementedError:
freq = getattr(self, "freqstr", getattr(self, "inferred_freq", None))
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In practice, I don't think we actually run into cases that need this. For example, freqstr for the DateOffset case gives:

In [3]: d.index.freq
Out[3]: <DateOffset: days=1>

In [4]: d.index.freqstr
Out[4]: '<DateOffset: days=1>'

This "<DateOffset: days=1>" string is never going to be useful. But in practice, it also seems that parsing.parse_time_string only actually uses freq in very few cases. From a quick look, it only seems to use it if it is exactly equal to "M", or in case of parsing quarters. Here I could create a snippet where passing the freq actually impacts the result:

In [6]: parsing.parse_time_string("4q2022", "A-DEC")
Out[6]: (datetime.datetime(2022, 10, 1, 0, 0), 'quarter')

In [7]: parsing.parse_time_string("4q2022", "A-NOV")
Out[7]: (datetime.datetime(2022, 9, 1, 0, 0), 'quarter')

But, so this only is for quarterly offsets, and those do define a rule_code, so you probably don't run into this issue with that kind of freqs.

This line freq = getattr(self, "freqstr", getattr(self, "inferred_freq", None)) is restoring what we did before #42149, so that's good for a regression fix in the bug-fix release. But we should maybe also see if we can just remove it later on (and just pass None here if rule_code isn't defined?)

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I checked passing None if rule_code isn't defined and a couple of tests fail in this case. Didn't look into it further though. But I think it should be possible to improve the situation around rule_code.

parsed, reso_str = parsing.parse_time_string(label, freq)
reso = Resolution.from_attrname(reso_str)
return parsed, reso

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43 changes: 43 additions & 0 deletions pandas/tests/frame/indexing/test_getitem.py
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Expand Up @@ -8,12 +8,14 @@
CategoricalDtype,
CategoricalIndex,
DataFrame,
DateOffset,
DatetimeIndex,
Index,
MultiIndex,
Series,
Timestamp,
concat,
date_range,
get_dummies,
period_range,
)
Expand Down Expand Up @@ -172,6 +174,47 @@ def test_getitem_iloc_two_dimensional_generator(self):
expected = Series([5, 6], name="b", index=[1, 2])
tm.assert_series_equal(result, expected)

def test_getitem_iloc_dateoffset_days(self):
# GH 46671
df = DataFrame(
list(range(10)),
index=date_range("01-01-2022", periods=10, freq=DateOffset(days=1)),
)
result = df.loc["2022-01-01":"2022-01-03"]
expected = DataFrame(
[0, 1, 2],
index=DatetimeIndex(
["2022-01-01", "2022-01-02", "2022-01-03"],
dtype="datetime64[ns]",
freq=DateOffset(days=1),
),
)
tm.assert_frame_equal(result, expected)

df = DataFrame(
list(range(10)),
index=date_range(
"01-01-2022", periods=10, freq=DateOffset(days=1, hours=2)
),
)
result = df.loc["2022-01-01":"2022-01-03"]
expected = DataFrame(
[0, 1, 2],
index=DatetimeIndex(
["2022-01-01 00:00:00", "2022-01-02 02:00:00", "2022-01-03 04:00:00"],
dtype="datetime64[ns]",
freq=DateOffset(days=1, hours=2),
),
)
tm.assert_frame_equal(result, expected)

df = DataFrame(
list(range(10)),
index=date_range("01-01-2022", periods=10, freq=DateOffset(minutes=3)),
)
result = df.loc["2022-01-01":"2022-01-03"]
tm.assert_frame_equal(result, df)


class TestGetitemCallable:
def test_getitem_callable(self, float_frame):
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