"""
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Tests for DateOffset additions over Daylight Savings Time
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"""
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from datetime import timedelta
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import pytest
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import pytz
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from pandas._libs.tslibs import Timestamp
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from pandas._libs.tslibs.offsets import (
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BMonthBegin,
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BMonthEnd,
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BQuarterBegin,
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BQuarterEnd,
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BYearBegin,
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BYearEnd,
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CBMonthBegin,
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CBMonthEnd,
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CustomBusinessDay,
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DateOffset,
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Day,
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MonthBegin,
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MonthEnd,
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QuarterBegin,
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QuarterEnd,
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SemiMonthBegin,
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SemiMonthEnd,
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Week,
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YearBegin,
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YearEnd,
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)
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from pandas.util.version import Version
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# error: Module has no attribute "__version__"
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pytz_version = Version(pytz.__version__) # type: ignore[attr-defined]
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def get_utc_offset_hours(ts):
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# take a Timestamp and compute total hours of utc offset
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o = ts.utcoffset()
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return (o.days * 24 * 3600 + o.seconds) / 3600.0
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class TestDST:
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# one microsecond before the DST transition
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ts_pre_fallback = "2013-11-03 01:59:59.999999"
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ts_pre_springfwd = "2013-03-10 01:59:59.999999"
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# test both basic names and dateutil timezones
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timezone_utc_offsets = {
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"US/Eastern": {"utc_offset_daylight": -4, "utc_offset_standard": -5},
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"dateutil/US/Pacific": {"utc_offset_daylight": -7, "utc_offset_standard": -8},
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}
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valid_date_offsets_singular = [
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"weekday",
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"day",
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"hour",
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"minute",
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"second",
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"microsecond",
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]
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valid_date_offsets_plural = [
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"weeks",
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"days",
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"hours",
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"minutes",
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"seconds",
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"milliseconds",
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"microseconds",
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]
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def _test_all_offsets(self, n, **kwds):
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valid_offsets = (
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self.valid_date_offsets_plural
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if n > 1
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else self.valid_date_offsets_singular
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)
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for name in valid_offsets:
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self._test_offset(offset_name=name, offset_n=n, **kwds)
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def _test_offset(self, offset_name, offset_n, tstart, expected_utc_offset):
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offset = DateOffset(**{offset_name: offset_n})
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t = tstart + offset
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if expected_utc_offset is not None:
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assert get_utc_offset_hours(t) == expected_utc_offset
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if offset_name == "weeks":
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# dates should match
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assert t.date() == timedelta(days=7 * offset.kwds["weeks"]) + tstart.date()
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# expect the same day of week, hour of day, minute, second, ...
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assert (
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t.dayofweek == tstart.dayofweek
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and t.hour == tstart.hour
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and t.minute == tstart.minute
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and t.second == tstart.second
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)
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elif offset_name == "days":
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# dates should match
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assert timedelta(offset.kwds["days"]) + tstart.date() == t.date()
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# expect the same hour of day, minute, second, ...
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assert (
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t.hour == tstart.hour
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and t.minute == tstart.minute
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and t.second == tstart.second
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)
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elif offset_name in self.valid_date_offsets_singular:
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# expect the singular offset value to match between tstart and t
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datepart_offset = getattr(
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t, offset_name if offset_name != "weekday" else "dayofweek"
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)
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assert datepart_offset == offset.kwds[offset_name]
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else:
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# the offset should be the same as if it was done in UTC
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assert t == (tstart.tz_convert("UTC") + offset).tz_convert("US/Pacific")
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def _make_timestamp(self, string, hrs_offset, tz):
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if hrs_offset >= 0:
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offset_string = f"{hrs_offset:02d}00"
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else:
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offset_string = f"-{(hrs_offset * -1):02}00"
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return Timestamp(string + offset_string).tz_convert(tz)
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def test_springforward_plural(self):
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# test moving from standard to daylight savings
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for tz, utc_offsets in self.timezone_utc_offsets.items():
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hrs_pre = utc_offsets["utc_offset_standard"]
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hrs_post = utc_offsets["utc_offset_daylight"]
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self._test_all_offsets(
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n=3,
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tstart=self._make_timestamp(self.ts_pre_springfwd, hrs_pre, tz),
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expected_utc_offset=hrs_post,
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)
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def test_fallback_singular(self):
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# in the case of singular offsets, we don't necessarily know which utc
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# offset the new Timestamp will wind up in (the tz for 1 month may be
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# different from 1 second) so we don't specify an expected_utc_offset
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for tz, utc_offsets in self.timezone_utc_offsets.items():
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hrs_pre = utc_offsets["utc_offset_standard"]
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self._test_all_offsets(
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n=1,
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tstart=self._make_timestamp(self.ts_pre_fallback, hrs_pre, tz),
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expected_utc_offset=None,
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)
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def test_springforward_singular(self):
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for tz, utc_offsets in self.timezone_utc_offsets.items():
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hrs_pre = utc_offsets["utc_offset_standard"]
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self._test_all_offsets(
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n=1,
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tstart=self._make_timestamp(self.ts_pre_springfwd, hrs_pre, tz),
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expected_utc_offset=None,
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)
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offset_classes = {
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MonthBegin: ["11/2/2012", "12/1/2012"],
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MonthEnd: ["11/2/2012", "11/30/2012"],
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BMonthBegin: ["11/2/2012", "12/3/2012"],
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BMonthEnd: ["11/2/2012", "11/30/2012"],
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CBMonthBegin: ["11/2/2012", "12/3/2012"],
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CBMonthEnd: ["11/2/2012", "11/30/2012"],
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SemiMonthBegin: ["11/2/2012", "11/15/2012"],
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SemiMonthEnd: ["11/2/2012", "11/15/2012"],
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Week: ["11/2/2012", "11/9/2012"],
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YearBegin: ["11/2/2012", "1/1/2013"],
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YearEnd: ["11/2/2012", "12/31/2012"],
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BYearBegin: ["11/2/2012", "1/1/2013"],
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BYearEnd: ["11/2/2012", "12/31/2012"],
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QuarterBegin: ["11/2/2012", "12/1/2012"],
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QuarterEnd: ["11/2/2012", "12/31/2012"],
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BQuarterBegin: ["11/2/2012", "12/3/2012"],
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BQuarterEnd: ["11/2/2012", "12/31/2012"],
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Day: ["11/4/2012", "11/4/2012 23:00"],
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}.items()
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@pytest.mark.parametrize("tup", offset_classes)
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def test_all_offset_classes(self, tup):
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offset, test_values = tup
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first = Timestamp(test_values[0], tz="US/Eastern") + offset()
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second = Timestamp(test_values[1], tz="US/Eastern")
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assert first == second
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@pytest.mark.parametrize(
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"original_dt, target_dt, offset, tz",
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[
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pytest.param(
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Timestamp("1900-01-01"),
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Timestamp("1905-07-01"),
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MonthBegin(66),
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"Africa/Kinshasa",
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marks=pytest.mark.xfail(
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pytz_version < Version("2020.5") or pytz_version == Version("2022.2"),
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reason="GH#41906: pytz utc transition dates changed",
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),
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),
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(
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Timestamp("2021-10-01 01:15"),
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Timestamp("2021-10-31 01:15"),
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MonthEnd(1),
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"Europe/London",
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),
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(
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Timestamp("2010-12-05 02:59"),
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Timestamp("2010-10-31 02:59"),
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SemiMonthEnd(-3),
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"Europe/Paris",
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),
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(
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Timestamp("2021-10-31 01:20"),
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Timestamp("2021-11-07 01:20"),
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CustomBusinessDay(2, weekmask="Sun Mon"),
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"US/Eastern",
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),
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(
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Timestamp("2020-04-03 01:30"),
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Timestamp("2020-11-01 01:30"),
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YearBegin(1, month=11),
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"America/Chicago",
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),
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],
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)
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def test_nontick_offset_with_ambiguous_time_error(original_dt, target_dt, offset, tz):
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# .apply for non-Tick offsets throws AmbiguousTimeError when the target dt
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# is dst-ambiguous
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localized_dt = original_dt.tz_localize(tz)
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msg = f"Cannot infer dst time from {target_dt}, try using the 'ambiguous' argument"
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with pytest.raises(pytz.AmbiguousTimeError, match=msg):
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localized_dt + offset
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