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ENH: DatetimeIndex.snap support non-nano #47537

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Merged
merged 1 commit into from
Jun 29, 2022
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ENH: DatetimeIndex.snap support non-nano #47537

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6 changes: 2 additions & 4 deletions pandas/core/indexes/datetimes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,6 @@
from pandas.util._exceptions import find_stack_level

from pandas.core.dtypes.common import (
DT64NS_DTYPE,
is_datetime64_dtype,
is_datetime64tz_dtype,
is_scalar,
Expand Down Expand Up @@ -552,7 +551,7 @@ def snap(self, freq="S") -> DatetimeIndex:
# Superdumb, punting on any optimizing
freq = to_offset(freq)

snapped = np.empty(len(self), dtype=DT64NS_DTYPE)
dta = self._data.copy()

for i, v in enumerate(self):
s = v
Expand All @@ -563,9 +562,8 @@ def snap(self, freq="S") -> DatetimeIndex:
s = t0
else:
s = t1
snapped[i] = s
dta[i] = s

dta = DatetimeArray(snapped, dtype=self.dtype)
return DatetimeIndex._simple_new(dta, name=self.name)

# --------------------------------------------------------------------
Expand Down
25 changes: 24 additions & 1 deletion pandas/tests/indexes/datetimes/methods/test_snap.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,10 +7,30 @@
import pandas._testing as tm


def astype_non_nano(dti_nano, unit):
# TODO(2.0): remove once DTI/DTA.astype supports non-nano
if unit == "ns":
return dti_nano

dta_nano = dti_nano._data
arr_nano = dta_nano._ndarray

arr = arr_nano.astype(f"M8[{unit}]")
if dti_nano.tz is None:
dtype = arr.dtype
else:
dtype = type(dti_nano.dtype)(tz=dti_nano.tz, unit=unit)
dta = type(dta_nano)._simple_new(arr, dtype=dtype)
dti = DatetimeIndex(dta, name=dti_nano.name)
assert dti.dtype == dtype
return dti


@pytest.mark.filterwarnings("ignore::DeprecationWarning")
@pytest.mark.parametrize("tz", [None, "Asia/Shanghai", "Europe/Berlin"])
@pytest.mark.parametrize("name", [None, "my_dti"])
def test_dti_snap(name, tz):
@pytest.mark.parametrize("unit", ["ns", "us", "ms", "s"])
def test_dti_snap(name, tz, unit):
dti = DatetimeIndex(
[
"1/1/2002",
Expand All @@ -25,10 +45,12 @@ def test_dti_snap(name, tz):
tz=tz,
freq="D",
)
dti = astype_non_nano(dti, unit)

result = dti.snap(freq="W-MON")
expected = date_range("12/31/2001", "1/7/2002", name=name, tz=tz, freq="w-mon")
expected = expected.repeat([3, 4])
expected = astype_non_nano(expected, unit)
tm.assert_index_equal(result, expected)
assert result.tz == expected.tz
assert result.freq is None
Expand All @@ -38,6 +60,7 @@ def test_dti_snap(name, tz):

expected = date_range("1/1/2002", "1/7/2002", name=name, tz=tz, freq="b")
expected = expected.repeat([1, 1, 1, 2, 2])
expected = astype_non_nano(expected, unit)
tm.assert_index_equal(result, expected)
assert result.tz == expected.tz
assert result.freq is None
Expand Down