Skip to content

BUG: PeriodIndex.from_fields rejects non-December quarterly freqs (#55784) #66553

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

Open
karandhaodiyal28-hash wants to merge 1 commit into
base: main
Choose a base branch
from
Open

BUG: PeriodIndex.from_fields rejects non-December quarterly freqs (#55784) #66553

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
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/v3.1.0.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -563,6 +563,7 @@ Period
- Bug in :meth:`Period.strftime` where unknown format directives (e.g. ``"%Q"``) silently produced platform-dependent output and crashed the Python process on Windows; an ``Invalid format string`` ``ValueError`` is now raised on all platforms (:issue:`53562`)
- Bug in :meth:`Period.to_timestamp` and :meth:`PeriodIndex.to_timestamp` returning incorrect timestamps when the target frequency normalized to nanoseconds (e.g. ``"1ns"``) or when converting a nanosecond ``Period`` to a coarser target frequency (:issue:`63760`)
- Bug in :meth:`Period.to_timestamp` and :meth:`PeriodIndex.to_timestamp` with ``how="end"`` losing nanosecond precision when the target frequency normalized to nanoseconds (e.g. ``"1ns"``); the target frequency is now also validated when ``how="end"`` (:issue:`63760`)
- Bug in :meth:`PeriodIndex.from_fields` raising ``AssertionError`` for a quarterly ``freq`` not anchored on December (e.g. ``QuarterEnd(startingMonth=2)``), even though the equivalent scalar :class:`Period` works (:issue:`55784`)
-

Plotting
Expand Down
2 changes: 1 addition & 1 deletion pandas/core/arrays/period.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1586,7 +1586,7 @@ def _range_from_fields(
else:
freq = to_offset(freq, is_period=True)
base = libperiod.freq_to_dtype_code(freq)
if base != FreqGroup.FR_QTR.value:
if FreqGroup.from_period_dtype_code(base) != FreqGroup.FR_QTR:
raise AssertionError("base must equal FR_QTR")

@jbrockmendel jbrockmendel Jul 31, 2026

Copy link
Copy Markdown
Member

Choose a reason for hiding this comment

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

is this reachable? if so, we should be raising something other than AssertionError


freqstr = freq.freqstr
Expand Down
10 changes: 10 additions & 0 deletions pandas/tests/indexes/period/test_constructors.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -212,6 +212,16 @@ def test_constructor_field_arrays(self):
exp = period_range("2007-01", periods=3, freq="M")
tm.assert_index_equal(idx, exp)

@pytest.mark.parametrize("starting_month", range(1, 13))
def test_from_fields_quarterly_non_december_anchor(self, starting_month):
# GH#55784 from_fields rejected any quarterly freq not anchored on
# December, even though the equivalent scalar Period works.
freq = offsets.QuarterEnd(startingMonth=starting_month)
result = PeriodIndex.from_fields(year=[2014], quarter=[3], freq=freq)
expected = Period(year=2014, quarter=3, freq=freq)
assert result[0] == expected
assert result.dtype == PeriodDtype(freq)

def test_constructor_nano(self):
idx = period_range(
start=Period(ordinal=1, freq="ns"),
Expand Down