import pytest
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from pandas._libs.tslibs.dtypes import NpyDatetimeUnit
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from pandas.errors import OutOfBoundsDatetime
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from pandas import Timestamp
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class TestTimestampAsUnit:
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def test_as_unit(self):
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ts = Timestamp("1970-01-01").as_unit("ns")
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assert ts.unit == "ns"
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assert ts.as_unit("ns") is ts
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res = ts.as_unit("us")
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assert res._value == ts._value // 1000
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assert res._creso == NpyDatetimeUnit.NPY_FR_us.value
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rt = res.as_unit("ns")
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assert rt._value == ts._value
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assert rt._creso == ts._creso
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res = ts.as_unit("ms")
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assert res._value == ts._value // 1_000_000
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assert res._creso == NpyDatetimeUnit.NPY_FR_ms.value
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rt = res.as_unit("ns")
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assert rt._value == ts._value
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assert rt._creso == ts._creso
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res = ts.as_unit("s")
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assert res._value == ts._value // 1_000_000_000
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assert res._creso == NpyDatetimeUnit.NPY_FR_s.value
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rt = res.as_unit("ns")
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assert rt._value == ts._value
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assert rt._creso == ts._creso
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def test_as_unit_overflows(self):
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# microsecond that would be just out of bounds for nano
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us = 9223372800000000
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ts = Timestamp._from_value_and_reso(us, NpyDatetimeUnit.NPY_FR_us.value, None)
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msg = "Cannot cast 2262-04-12 00:00:00 to unit='ns' without overflow"
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with pytest.raises(OutOfBoundsDatetime, match=msg):
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ts.as_unit("ns")
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res = ts.as_unit("ms")
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assert res._value == us // 1000
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assert res._creso == NpyDatetimeUnit.NPY_FR_ms.value
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def test_as_unit_rounding(self):
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ts = Timestamp(1_500_000) # i.e. 1500 microseconds
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res = ts.as_unit("ms")
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expected = Timestamp(1_000_000) # i.e. 1 millisecond
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assert res == expected
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assert res._creso == NpyDatetimeUnit.NPY_FR_ms.value
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assert res._value == 1
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with pytest.raises(ValueError, match="Cannot losslessly convert units"):
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ts.as_unit("ms", round_ok=False)
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def test_as_unit_non_nano(self):
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# case where we are going neither to nor from nano
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ts = Timestamp("1970-01-02").as_unit("ms")
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assert ts.year == 1970
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assert ts.month == 1
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assert ts.day == 2
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assert ts.hour == ts.minute == ts.second == ts.microsecond == ts.nanosecond == 0
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res = ts.as_unit("s")
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assert res._value == 24 * 3600
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assert res.year == 1970
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assert res.month == 1
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assert res.day == 2
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assert (
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res.hour
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== res.minute
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== res.second
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== res.microsecond
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== res.nanosecond
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== 0
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)
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