Skip to content

BUG: DateTimeIndex.is_year_start unexpected behavior when constructed with freq 'MS' date_range (#57377) #57494

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 16 commits into from
Jun 8, 2024
Merged

BUG: DateTimeIndex.is_year_start unexpected behavior when constructed with freq 'MS' date_range (#57377) #57494

Show file tree
Hide file tree
Changes from 12 commits
Commits
Show all changes
16 commits
Select commit Hold shift + click to select a range
fc42033
Added some comments to where the bug is occurring
mattheeter Feb 18, 2024
29ecfda
Potential fix, passed all potentially relevant tests
mattheeter Feb 18, 2024
3302622
Very likely fix
mattheeter Feb 18, 2024
6e9be5b
Reverted ro previous start/end scheme; added tests
mattheeter Feb 18, 2024
f68f41c
Merge branch 'pandas-dev:main' into bug/is_year_start
mattheeter Feb 18, 2024
bd1d878
Added fixes to whatsnew doc
mattheeter Feb 18, 2024
6e4be2e
Removed stray comment
mattheeter Feb 19, 2024
248cab0
Merge branch 'main' into bug/is_year_start
mattheeter Feb 20, 2024
ad08b78
Merge branch 'main' into bug/is_year_start
mattheeter Feb 20, 2024
ccbdfe2
Merge branch 'main' into bug/is_year_start
mattheeter Feb 20, 2024
b0c7bf1
Merge branch 'main' into bug/is_year_start
mattheeter Apr 22, 2024
3c5fab0
Fixed alphabetical problem in whatsnew
mattheeter Apr 22, 2024
2c96c49
Merge remote-tracking branch 'upstream/main' into bug/is_year_start
MarcoGorelli Jun 6, 2024
7f98a6a
add parametric test
MarcoGorelli Jun 6, 2024
3cc7ea6
Merge branch 'bug/is_year_start' of github.com:mattheeter/pandas into…
MarcoGorelli Jun 6, 2024
74f151e
fixup
MarcoGorelli Jun 6, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions doc/source/whatsnew/v3.0.0.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -356,6 +356,7 @@ Categorical

Datetimelike
^^^^^^^^^^^^
- Bug in :attr:`is_year_start` where a DateTimeIndex constructed via a date_range with frequency 'MS' wouldn't have the correct year or quarter start attributes (:issue:`57377`)
- Bug in :class:`Timestamp` constructor failing to raise when ``tz=None`` is explicitly specified in conjunction with timezone-aware ``tzinfo`` or data (:issue:`48688`)
- Bug in :func:`date_range` where the last valid timestamp would sometimes not be produced (:issue:`56134`)
- Bug in :func:`date_range` where using a negative frequency value would not include all points between the start and end values (:issue:`56382`)
Expand Down
6 changes: 4 additions & 2 deletions pandas/_libs/tslibs/fields.pyx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -253,10 +253,12 @@ def get_start_end_field(
# month of year. Other offsets use month, startingMonth as ending
# month of year.

if (freqstr[0:2] in ["MS", "QS", "YS"]) or (
freqstr[1:3] in ["MS", "QS", "YS"]):
# According to the above comment, the first conditional is for QS and YS only
if (freqstr[0:2] in ["QS", "YS"]) or (
freqstr[1:3] in ["QS", "YS"]):
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

this logic is already broken on main - it seems to assume that n is only a single digit

and so it produces this kind of nonsense:

In [39]: dr = pd.date_range("2017-01-01", periods=2, freq="7YS")

In [40]: dr
Out[40]: DatetimeIndex(['2017-01-01', '2024-01-01'], dtype='datetime64[ns]', freq='7YS-JAN')

In [41]: dr.is_year_start
Out[41]: array([ True,  True])

In [42]: dr = pd.date_range("2017-01-01", periods=2, freq="10YS")

In [43]: dr
Out[43]: DatetimeIndex(['2017-01-01', '2027-01-01'], dtype='datetime64[ns]', freq='10YS-JAN')

In [44]: dr.is_year_start
Out[44]: array([False, False])

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

wow, looks like this broken logic was introduced 13 years ago... 😭

https://github.com/pandas-dev/pandas/pull/4823/files

end_month = 12 if month_kw == 1 else month_kw - 1
start_month = month_kw

else:
end_month = month_kw
start_month = (end_month % 12) + 1
Expand Down
2 changes: 1 addition & 1 deletion pandas/core/arrays/datetimes.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -143,7 +143,7 @@ def f(self):
month_kw = 12
if freq:
kwds = freq.kwds
month_kw = kwds.get("startingMonth", kwds.get("month", 12))
month_kw = kwds.get("startingMonth", kwds.get("month", month_kw))

result = fields.get_start_end_field(
values, field, self.freqstr, month_kw, reso=self._creso
Expand Down
78 changes: 78 additions & 0 deletions pandas/tests/indexes/datetimes/test_scalar_compat.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -328,3 +328,81 @@ def test_dti_is_month_start_custom(self):
msg = "Custom business days is not supported by is_month_start"
with pytest.raises(ValueError, match=msg):
dti.is_month_start

@pytest.mark.parametrize(
"timestamp, freq, periods, expected_values",
[
("2017-12-01", "MS", 3, np.array([False, True, False])),
("2017-12-01", "QS", 3, np.array([True, False, False])),
("2017-12-01", "YS", 3, np.array([True, True, True])),
],
)
def test_dti_dr_is_year_start(self, timestamp, freq, periods, expected_values):
# GH57377
result = date_range(timestamp, freq=freq, periods=periods).is_year_start
tm.assert_numpy_array_equal(result, expected_values)

@pytest.mark.parametrize(
"timestamp, freq, periods, expected_values",
[
("2017-12-01", "ME", 3, np.array([True, False, False])),
("2017-12-01", "QE", 3, np.array([True, False, False])),
("2017-12-01", "YE", 3, np.array([True, True, True])),
],
)
def test_dti_dr_is_year_end(self, timestamp, freq, periods, expected_values):
# GH57377
result = date_range(timestamp, freq=freq, periods=periods).is_year_end
tm.assert_numpy_array_equal(result, expected_values)

@pytest.mark.parametrize(
"timestamp, freq, periods, expected_values",
[
("2017-12-01", "MS", 3, np.array([False, True, False])),
("2017-12-01", "QS", 3, np.array([True, True, True])),
("2017-12-01", "YS", 3, np.array([True, True, True])),
],
)
def test_dti_dr_is_quarter_start(self, timestamp, freq, periods, expected_values):
# GH57377
result = date_range(timestamp, freq=freq, periods=periods).is_quarter_start
tm.assert_numpy_array_equal(result, expected_values)

@pytest.mark.parametrize(
"timestamp, freq, periods, expected_values",
[
("2017-12-01", "ME", 3, np.array([True, False, False])),
("2017-12-01", "QE", 3, np.array([True, True, True])),
("2017-12-01", "YE", 3, np.array([True, True, True])),
],
)
def test_dti_dr_is_quarter_end(self, timestamp, freq, periods, expected_values):
# GH57377
result = date_range(timestamp, freq=freq, periods=periods).is_quarter_end
tm.assert_numpy_array_equal(result, expected_values)

@pytest.mark.parametrize(
"timestamp, freq, periods, expected_values",
[
("2017-12-01", "MS", 3, np.array([True, True, True])),
("2017-12-01", "QS", 3, np.array([True, True, True])),
("2017-12-01", "YS", 3, np.array([True, True, True])),
],
)
def test_dti_dr_is_month_start(self, timestamp, freq, periods, expected_values):
# GH57377
result = date_range(timestamp, freq=freq, periods=periods).is_month_start
tm.assert_numpy_array_equal(result, expected_values)

@pytest.mark.parametrize(
"timestamp, freq, periods, expected_values",
[
("2017-12-01", "ME", 3, np.array([True, True, True])),
("2017-12-01", "QE", 3, np.array([True, True, True])),
("2017-12-01", "YE", 3, np.array([True, True, True])),
],
)
def test_dti_dr_is_month_end(self, timestamp, freq, periods, expected_values):
# GH57377
result = date_range(timestamp, freq=freq, periods=periods).is_month_end
tm.assert_numpy_array_equal(result, expected_values)
Loading