https://github.com/python/cpython/commit/6f9c76d8d86997012acfa09fed05396aa9349bbf commit: 6f9c76d8d86997012acfa09fed05396aa9349bbf branch: main author: tonghuaroot (童话) <[email protected]> committer: StanFromIreland <[email protected]> date: 2026-06-25T10:15:28+01:00 summary:
gh-152079: Fix `_datetime.fromisoformat()` mishandling a sub-second tz offset (#152087) Co-authored-by: Stan Ulbrych <[email protected]> files: A Misc/NEWS.d/next/Library/2026-06-24-12-00-00.gh-issue-152079.f1tzus.rst M Lib/test/datetimetester.py M Modules/_datetimemodule.c diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py index e29f5e3ecb5fd4..28c3ab2605c45d 100644 --- a/Lib/test/datetimetester.py +++ b/Lib/test/datetimetester.py @@ -3803,6 +3803,32 @@ def test_fromisoformat_utc(self): self.assertIs(dt.tzinfo, timezone.utc) + def test_fromisoformat_utc_subsecond_offset(self): + # A UTC offset whose whole-second part is zero but with a non-zero + # microsecond part must be preserved, not collapsed to UTC. + for us in (1, -1, 999999, -999999): + with self.subTest(microseconds=us): + tz = timezone(timedelta(microseconds=us)) + dt = self.theclass(2020, 6, 15, 12, 34, 56, tzinfo=tz) + rt = self.theclass.fromisoformat(dt.isoformat()) + self.assertEqual(rt.utcoffset(), timedelta(microseconds=us)) + self.assertEqual(rt, dt) + self.assertIsNot(rt.tzinfo, timezone.utc) + + tz = timezone(timedelta(hours=5, minutes=30, seconds=15, + microseconds=123456)) + dt = self.theclass(2020, 6, 15, 12, 34, 56, tzinfo=tz) + rt = self.theclass.fromisoformat(dt.isoformat()) + self.assertEqual(rt.utcoffset(), tz.utcoffset(None)) + self.assertEqual(rt, dt) + + for tstr in ('2020-06-15T12:34:56+00:00', + '2020-06-15T12:34:56+00:00:00.000000', + '2020-06-15T12:34:56Z'): + with self.subTest(tstr=tstr): + self.assertIs(self.theclass.fromisoformat(tstr).tzinfo, + timezone.utc) + def test_fromisoformat_subclass(self): class DateTimeSubclass(self.theclass): pass diff --git a/Misc/NEWS.d/next/Library/2026-06-24-12-00-00.gh-issue-152079.f1tzus.rst b/Misc/NEWS.d/next/Library/2026-06-24-12-00-00.gh-issue-152079.f1tzus.rst new file mode 100644 index 00000000000000..492d00724f6a46 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-06-24-12-00-00.gh-issue-152079.f1tzus.rst @@ -0,0 +1,3 @@ +Fix :meth:`datetime.datetime.fromisoformat` in the C implementation dropping +the sub-second part of a UTC offset whose whole-second part is zero, matching +the pure-Python implementation. diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c index 979aa1beb8657b..fd8d95d05c933e 100644 --- a/Modules/_datetimemodule.c +++ b/Modules/_datetimemodule.c @@ -1668,8 +1668,8 @@ tzinfo_from_isoformat_results(int rv, int tzoffset, int tz_useconds) { PyObject *tzinfo; if (rv == 1) { - // Create a timezone from offset in seconds (0 returns UTC) - if (tzoffset == 0) { + // Create a timezone from the offset (a zero offset returns UTC) + if (tzoffset == 0 && tz_useconds == 0) { return Py_NewRef(CONST_UTC(NO_STATE)); } _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
