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BUG: DataFrame/Series.tz_convert does not modifies original data with copy=False #24657

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Jan 8, 2019
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BUG: DataFrame/Series.tz_convert does not modifies original data with copy=False #24657

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BUG: DataFrame/Series.tz_localize/convert with copy=False does not mu…
Jan 7, 2019
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.24.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1596,6 +1596,7 @@ Timezones
- Bug in :func:`to_datetime` where ``utc=True`` was not respected when passing a :class:`Timestamp` (:issue:`24415`)
- Bug in :meth:`DataFrame.any` returns wrong value when ``axis=1`` and the data is of datetimelike type (:issue:`23070`)
- Bug in :meth:`DatetimeIndex.to_period` where a timezone aware index was converted to UTC first before creating :class:`PeriodIndex` (:issue:`22905`)
- Bug in :meth:`DataFrame.tz_localize`, :meth:`DataFrame.tz_convert`, :meth:`Series.tz_localize`, and :meth:`Series.tz_convert` where ``copy=False`` would mutate the original argument inplace (:issue:`6326`)

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^^^^^^^
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4 changes: 2 additions & 2 deletions pandas/core/generic.py
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Expand Up @@ -9226,7 +9226,7 @@ def _tz_convert(ax, tz):
ax = _tz_convert(ax, tz)

result = self._constructor(self._data, copy=copy)
result.set_axis(ax, axis=axis, inplace=True)
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this should really have the inplace arg rather than copy as that is the meaning here.

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not sure if we should change this api though as don’t really love inplace generally

result = result.set_axis(ax, axis=axis, inplace=False)
return result.__finalize__(self)

def tz_localize(self, tz, axis=0, level=None, copy=True,
Expand Down Expand Up @@ -9390,7 +9390,7 @@ def _tz_localize(ax, tz, ambiguous, nonexistent):
ax = _tz_localize(ax, tz, ambiguous, nonexistent)

result = self._constructor(self._data, copy=copy)
result.set_axis(ax, axis=axis, inplace=True)
result = result.set_axis(ax, axis=axis, inplace=False)
return result.__finalize__(self)

# ----------------------------------------------------------------------
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16 changes: 16 additions & 0 deletions pandas/tests/frame/test_timezones.py
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Expand Up @@ -180,3 +180,19 @@ def test_boolean_compare_transpose_tzindex_with_dst(self, tz):
result = df.T == df.T
expected = DataFrame(True, index=list('ab'), columns=idx)
tm.assert_frame_equal(result, expected)

@pytest.mark.parametrize('copy', [True, False])
@pytest.mark.parametrize('method, tz', [
['tz_localize', None],
['tz_convert', 'Europe/Berlin']
])
def test_tz_localize_convert_copy_inplace_mutate(self, copy, method, tz):
# GH 6326
result = DataFrame(np.arange(0, 5),
index=date_range('20131027', periods=5,
freq='1H', tz=tz))
getattr(result, method)('UTC', copy=copy)
expected = DataFrame(np.arange(0, 5),
index=date_range('20131027', periods=5,
freq='1H', tz=tz))
tm.assert_frame_equal(result, expected)
16 changes: 16 additions & 0 deletions pandas/tests/series/test_timezones.py
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Expand Up @@ -348,3 +348,19 @@ def test_series_truncate_datetimeindex_tz(self):
result = s.truncate(datetime(2005, 4, 2), datetime(2005, 4, 4))
expected = Series([1, 2, 3], index=idx[1:4])
tm.assert_series_equal(result, expected)

@pytest.mark.parametrize('copy', [True, False])
@pytest.mark.parametrize('method, tz', [
['tz_localize', None],
['tz_convert', 'Europe/Berlin']
])
def test_tz_localize_convert_copy_inplace_mutate(self, copy, method, tz):
# GH 6326
result = Series(np.arange(0, 5),
index=date_range('20131027', periods=5, freq='1H',
tz=tz))
getattr(result, method)('UTC', copy=copy)
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@mroeschke i'm confused by this; wouldn't we expect the tz in expected.index to be UTC, not tz

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The naming of the test is a bit confusing, but this call here should not be an inplace operation.

I'm checking that the original data result was not modified after calling tz_localize/tz_convert with copy

#6326 (comment)

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ahh i see. ill update #37498 appropriately

expected = Series(np.arange(0, 5),
index=date_range('20131027', periods=5, freq='1H',
tz=tz))
tm.assert_series_equal(result, expected)