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ENH: Add lazy copy for tz_convert and tz_localize #50490

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Merged
merged 1 commit into from
Jan 3, 2023
Merged

ENH: Add lazy copy for tz_convert and tz_localize #50490

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4 changes: 2 additions & 2 deletions pandas/core/generic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10099,7 +10099,7 @@ def truncate(
@final
@doc(klass=_shared_doc_kwargs["klass"])
def tz_convert(
self: NDFrameT, tz, axis: Axis = 0, level=None, copy: bool_t = True
self: NDFrameT, tz, axis: Axis = 0, level=None, copy: bool_t | None = None
) -> NDFrameT:
"""
Convert tz-aware axis to target time zone.
Expand Down Expand Up @@ -10181,7 +10181,7 @@ def tz_localize(
tz,
axis: Axis = 0,
level=None,
copy: bool_t = True,
copy: bool_t | None = None,
ambiguous: TimeAmbiguous = "raise",
nonexistent: TimeNonexistent = "raise",
) -> NDFrameT:
Expand Down
23 changes: 23 additions & 0 deletions pandas/tests/copy_view/test_methods.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
DataFrame,
MultiIndex,
Series,
date_range,
)
import pandas._testing as tm
from pandas.tests.copy_view.util import get_array
Expand Down Expand Up @@ -441,6 +442,28 @@ def test_frame_set_axis(using_copy_on_write):
tm.assert_frame_equal(df, df_orig)


@pytest.mark.parametrize(
"func, tz", [("tz_convert", "Europe/Berlin"), ("tz_localize", None)]
)
def test_tz_convert_localize(using_copy_on_write, func, tz):
# GH 49473
ser = Series(
[1, 2], index=date_range(start="2014-08-01 09:00", freq="H", periods=2, tz=tz)
)
ser_orig = ser.copy()
ser2 = getattr(ser, func)("US/Central")

if using_copy_on_write:
assert np.shares_memory(ser.values, ser2.values)
else:
assert not np.shares_memory(ser.values, ser2.values)

# mutating ser triggers a copy-on-write for the column / block
ser2.iloc[0] = 0
assert not np.shares_memory(ser2.values, ser.values)
tm.assert_series_equal(ser, ser_orig)


def test_series_set_axis(using_copy_on_write):
# GH 49473
ser = Series([1, 2, 3])
Expand Down