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Merged
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Nov 5, 2018
Merged

BUG: Avoid casting to double type unnecessarily when setting values i… #23462

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BUG: Avoid casting to double type unnecessarily when setting values i…
icexelloss Nov 2, 2018
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icexelloss Nov 5, 2018
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.24.0.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -1210,6 +1210,7 @@ Indexing
- :class:`Index` no longer mangles ``None``, ``NaN`` and ``NaT``, i.e. they are treated as three different keys. However, for numeric Index all three are still coerced to a ``NaN`` (:issue:`22332`)
- Bug in `scalar in Index` if scalar is a float while the ``Index`` is of integer dtype (:issue:`22085`)
- Bug in `MultiIndex.set_levels` when levels value is not subscriptable (:issue:`23273`)
- Bug where setting a timedelta column by ``Index`` causes it to be casted to double, and therefore lose precision (:issue:`23511`)

Missing
^^^^^^^
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4 changes: 2 additions & 2 deletions pandas/core/internals/blocks.py
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Expand Up @@ -2104,9 +2104,9 @@ def _box_func(self):
def _can_hold_element(self, element):
tipo = maybe_infer_dtype_type(element)
if tipo is not None:
return issubclass(tipo.type, np.timedelta64)
return issubclass(tipo.type, (np.timedelta64, np.int64))
return is_integer(element) or isinstance(
element, (timedelta, np.timedelta64))
element, (timedelta, np.timedelta64, np.int64))

def fillna(self, value, **kwargs):

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15 changes: 15 additions & 0 deletions pandas/tests/indexing/test_timedelta.py
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Expand Up @@ -80,3 +80,18 @@ def test_numpy_timedelta_scalar_indexing(self, start, stop,
result = s.loc[slice(start, stop)]
expected = s.iloc[expected_slice]
tm.assert_series_equal(result, expected)

def test_roundtrip_thru_setitem(self):
# PR 23462
dt1 = pd.Timedelta(0)
dt2 = pd.Timedelta(28767471428571405)
df = pd.DataFrame({'dt': pd.Series([dt1, dt2])})
df_copy = df.copy()
s = pd.Series([dt1])

expected = df['dt'].iloc[1].value
df.loc[[True, False]] = s
result = df['dt'].iloc[1].value

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can you also test

tm.assert_frame_equal(df, df_copy)

(and copy df on line 89)

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Added

assert expected == result
tm.assert_frame_equal(df, df_copy)