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gh-99772: Do not ignore utc offset microseconds #99774

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gh-99772: Do not ignore utc offset microseconds #99774

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gh-99772: Do not ignore utc offset microseconds
blenq Nov 25, 2022
9079ad3
📜🤖 Added by blurb_it.
blurb-it[bot] Nov 25, 2022
08766ad
gh-99772: Fix for Windows
blenq Nov 25, 2022
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14 changes: 10 additions & 4 deletions Lib/datetime.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1466,10 +1466,16 @@ def _cmp(self, other, allow_mixed=False):
return 2 # arbitrary non-zero value
else:
raise TypeError("cannot compare naive and aware times")
myhhmm = self._hour * 60 + self._minute - myoff//timedelta(minutes=1)
othhmm = other._hour * 60 + other._minute - otoff//timedelta(minutes=1)
return _cmp((myhhmm, self._second, self._microsecond),
(othhmm, other._second, other._microsecond))

mydelta = timedelta(
seconds=self._hour * 3600 + self._minute * 60 + self._second,
microseconds=self._microsecond
) - myoff
otdelta = timedelta(
seconds=other._hour * 3600 + other._minute * 60 + other._second,
microseconds=other._microsecond
) - otoff
return _cmp(mydelta, otdelta)

def __hash__(self):
"""Hash."""
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16 changes: 16 additions & 0 deletions Lib/test/datetimetester.py
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Expand Up @@ -3861,6 +3861,22 @@ def utcoffset(self, t):
expected = 1
self.assertEqual(got, expected)

# Test tz offset with microseconds
d0 = base.replace(minute=5, tzinfo=timezone(timedelta(microseconds=3)))
d1 = base.replace(
minute=5, tzinfo=timezone(timedelta(microseconds=456)))
d2 = base.replace(
minute=5, tzinfo=timezone(timedelta(microseconds=98764)))
for x in d0, d1, d2:
for y in d0, d1, d2:
for op in lt, le, gt, ge, eq, ne:
got = op(x, y)
expected = op(
-x.utcoffset().microseconds,

@Jason-Y-Z Jason-Y-Z Nov 27, 2022

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why do we need the minus sign here?

@blenq blenq Nov 27, 2022

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Because the utc offset contributes to the time in a negative way, in other words, the greater the utc offset, the earlier the actual time.

-y.utcoffset().microseconds)
self.assertEqual(got, expected)



# Testing time objects with a non-None tzinfo.
class TestTimeTZ(TestTime, TZInfoBase, unittest.TestCase):
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2022-11-25-12-25-29.gh-issue-99772.ZO23Uc.rst
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@@ -0,0 +1 @@
Fix compare operations for datetime.time values with microseconds resolution in utcoffset.
32 changes: 17 additions & 15 deletions Modules/_datetimemodule.c
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Expand Up @@ -4473,22 +4473,24 @@ time_richcompare(PyObject *self, PyObject *other, int op)
}
/* The hard case: both aware with different UTC offsets */
else if (offset1 != Py_None && offset2 != Py_None) {
int offsecs1, offsecs2;
int64_t offusecs1, offusecs2, diff64;

@Jason-Y-Z Jason-Y-Z Nov 27, 2022

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This might be a minor discussion point, but we could avoid using int64_t and the following big-integer calculations by doing a multi-step comparison, i.e. comparing the hours, then minutes, then seconds etc.
The motivation for this is a bit of gut feeling, but I think that way will be slightly more efficient in terms of time and space.

@blenq blenq Nov 27, 2022 •
edited
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I actually implemented it like you suggest earlier, because I share your gut feeling. Using the existing code for checks up to seconds and adjusting only the microseconds check. Indeed with the advantage that it all fits in 32 bits.

What I encountered using this approach was the following: 13:59:59.9+02 is actually later than 14:00:00+02:00:00.9. The combined microseconds values, in the time values and the offsets, can contribute up to a maximum of 1.999998 seconds to the diff in either way. That means that the simple intermediary check that is used in other multi step comparisons if (diff == 0) can not be used. It should become if (diff > -2 && diff < 2). I chose to go for the int64_t approach because I thought it to be less confusing, than the 2 seconds intermediary check, but I am perfectly willing to go with your suggestion, if that is the consensus.

@pganssle pganssle Apr 24, 2023

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@blenq Does one of the tests already handle the use case of 13:59:59.9+02 vs. 14:00:00+02:00:00.9? If not we should add that as a test case.

assert(offset1 != offset2); /* else last "if" handled it */
offsecs1 = TIME_GET_HOUR(self) * 3600 +
TIME_GET_MINUTE(self) * 60 +
TIME_GET_SECOND(self) -
GET_TD_DAYS(offset1) * 86400 -
GET_TD_SECONDS(offset1);
offsecs2 = TIME_GET_HOUR(other) * 3600 +
TIME_GET_MINUTE(other) * 60 +
TIME_GET_SECOND(other) -
GET_TD_DAYS(offset2) * 86400 -
GET_TD_SECONDS(offset2);
diff = offsecs1 - offsecs2;
if (diff == 0)
diff = TIME_GET_MICROSECOND(self) -
TIME_GET_MICROSECOND(other);
offusecs1 = TIME_GET_HOUR(self) * INT64_C(3600000000) +
TIME_GET_MINUTE(self) * INT64_C(60000000) +
TIME_GET_SECOND(self) * 1000000 +
TIME_GET_MICROSECOND(self) -
GET_TD_DAYS(offset1) * 86400000000 -
GET_TD_SECONDS(offset1) * INT64_C(1000000) -
GET_TD_MICROSECONDS(offset1);
offusecs2 = TIME_GET_HOUR(other) * INT64_C(3600000000) +
TIME_GET_MINUTE(other) * INT64_C(60000000) +
TIME_GET_SECOND(other) * 1000000 +
TIME_GET_MICROSECOND(other) -
GET_TD_DAYS(offset2) * 86400000000 -
GET_TD_SECONDS(offset2) * INT64_C(1000000) -
GET_TD_MICROSECONDS(offset2);
diff64 = offusecs1 - offusecs2;
diff = diff64 ? diff64 < 0 ? -1 : 1 : 0; /* diff_to_bool needs int */
result = diff_to_bool(diff, op);
}
else if (op == Py_EQ) {
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