BUG: Timedelta components no longer rounded with high precision integers (#31380)

* BUG: Timedelta components no longer rounded with high precision integers

* Simplify NaT.total_seconds

* Also simplify another tz conversion code path

Author: mroeschke

doc/source/whatsnew/v1.1.0.rst

@@ -109,7 +109,7 @@ Datetimelike
 Timedelta
 ^^^^^^^^^
 
--
+- Bug in constructing a :class:`Timedelta` with a high precision integer that would round the :class:`Timedelta` components (:issue:`31354`)
 -
 
 Timezones

pandas/_libs/tslibs/conversion.pyx

@@ -29,7 +29,7 @@ from pandas._libs.tslibs.util cimport (
 from pandas._libs.tslibs.timedeltas cimport cast_from_unit
 from pandas._libs.tslibs.timezones cimport (
     is_utc, is_tzlocal, is_fixed_offset, get_utcoffset, get_dst_info,
-    get_timezone, maybe_get_tz, tz_compare, treat_tz_as_dateutil)
+    get_timezone, maybe_get_tz, tz_compare)
 from pandas._libs.tslibs.timezones import UTC
 from pandas._libs.tslibs.parsing import parse_datetime_string
 
@@ -341,14 +341,6 @@ cdef _TSObject convert_datetime_to_tsobject(datetime ts, object tz,
             obj.tzinfo = tz
     else:
         obj.value = pydatetime_to_dt64(ts, &obj.dts)
-        # GH 24329 When datetime is ambiguous,
-        # pydatetime_to_dt64 doesn't take DST into account
-        # but with dateutil timezone, get_utcoffset does
-        # so we need to correct for it
-        if treat_tz_as_dateutil(ts.tzinfo):
-            if ts.tzinfo.is_ambiguous(ts):
-                dst_offset = ts.tzinfo.dst(ts)
-                obj.value += int(dst_offset.total_seconds() * 1e9)
         obj.tzinfo = ts.tzinfo
 
     if obj.tzinfo is not None and not is_utc(obj.tzinfo):

pandas/_libs/tslibs/nattype.pyx

@@ -2,7 +2,7 @@ from cpython.object cimport (
     PyObject_RichCompare,
     Py_GT, Py_GE, Py_EQ, Py_NE, Py_LT, Py_LE)
 
-from cpython.datetime cimport (datetime,
+from cpython.datetime cimport (datetime, timedelta,
                                PyDateTime_Check, PyDelta_Check,
                                PyDateTime_IMPORT)
 
@@ -276,13 +276,6 @@ cdef class _NaT(datetime):
     def __long__(self):
         return NPY_NAT
 
-    def total_seconds(self):
-        """
-        Total duration of timedelta in seconds (to microsecond precision).
-        """
-        # GH#10939
-        return np.nan
-
     @property
     def is_leap_year(self):
         return False
@@ -386,6 +379,7 @@ class NaTType(_NaT):
     # nan methods
     weekday = _make_nan_func('weekday', datetime.weekday.__doc__)
     isoweekday = _make_nan_func('isoweekday', datetime.isoweekday.__doc__)
+    total_seconds = _make_nan_func('total_seconds', timedelta.total_seconds.__doc__)
     month_name = _make_nan_func('month_name',  # noqa:E128
         """
         Return the month name of the Timestamp with specified locale.

pandas/_libs/tslibs/timedeltas.pyx

@@ -859,14 +859,6 @@ cdef class _Timedelta(timedelta):
         """
         return self.to_timedelta64()
 
-    def total_seconds(self):
-        """
-        Total duration of timedelta in seconds (to microsecond precision).
-        """
-        # GH 31043
-        # Microseconds precision to avoid confusing tzinfo.utcoffset
-        return (self.value - self.value % 1000) / 1e9
-
     def view(self, dtype):
         """
         Array view compatibility.
@@ -1250,7 +1242,7 @@ class Timedelta(_Timedelta):
             return NaT
 
         # make timedelta happy
-        td_base = _Timedelta.__new__(cls, microseconds=int(value) / 1000)
+        td_base = _Timedelta.__new__(cls, microseconds=int(value) // 1000)
         td_base.value = value
         td_base.is_populated = 0
         return td_base

pandas/tests/scalar/timedelta/test_timedelta.py

@@ -821,3 +821,16 @@ def test_resolution_deprecated(self):
 def test_truthiness(value, expected):
     # https://github.com/pandas-dev/pandas/issues/21484
     assert bool(value) is expected
+
+
+def test_timedelta_attribute_precision():
+    # GH 31354
+    td = Timedelta(1552211999999999872, unit="ns")
+    result = td.days * 86400
+    result += td.seconds
+    result *= 1000000
+    result += td.microseconds
+    result *= 1000
+    result += td.nanoseconds
+    expected = td.value
+    assert result == expected

pandas/tests/scalar/timestamp/test_timestamp.py

@@ -2,7 +2,6 @@
 
 import calendar
 from datetime import datetime, timedelta
-from distutils.version import LooseVersion
 import locale
 import unicodedata
 
@@ -1088,20 +1087,13 @@ def test_constructor_ambigous_dst():
     assert result == expected
 
 
-@pytest.mark.xfail(
-    LooseVersion(compat._optional._get_version(dateutil)) < LooseVersion("2.7.0"),
-    reason="dateutil moved to Timedelta.total_seconds() in 2.7.0",
-)
 @pytest.mark.parametrize("epoch", [1552211999999999872, 1552211999999999999])
 def test_constructor_before_dst_switch(epoch):
     # GH 31043
     # Make sure that calling Timestamp constructor
     # on time just before DST switch doesn't lead to
     # nonexistent time or value change
-    # Works only with dateutil >= 2.7.0 as dateutil overrid
-    # pandas.Timedelta.total_seconds with
-    # datetime.timedelta.total_seconds before
-    ts = Timestamp(epoch, tz="dateutil/US/Pacific")
+    ts = Timestamp(epoch, tz="dateutil/America/Los_Angeles")
     result = ts.tz.dst(ts)
     expected = timedelta(seconds=0)
     assert Timestamp(ts).value == epoch