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Revert change to comparison op with datetime.date objects (pandas-dev…
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TomAugspurger authored and david-liu-brattle-1 committed Jun 18, 2018
1 parent de162fc commit 9d9b473
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41 changes: 41 additions & 0 deletions doc/source/whatsnew/v0.23.1.txt
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,47 @@ and bug fixes. We recommend that all users upgrade to this version.
Fixed Regressions
~~~~~~~~~~~~~~~~~

**Comparing Series with datetime.date**

We've reverted a 0.23.0 change to comparing a :class:`Series` holding datetimes and a ``datetime.date`` object (:issue:`21152`).
In pandas 0.22 and earlier, comparing a Series holding datetimes and ``datetime.date`` objects would coerce the ``datetime.date`` to a datetime before comapring.
This was inconsistent with Python, NumPy, and :class:`DatetimeIndex`, which never consider a datetime and ``datetime.date`` equal.

In 0.23.0, we unified operations between DatetimeIndex and Series, and in the process changed comparisons between a Series of datetimes and ``datetime.date`` without warning.

We've temporarily restored the 0.22.0 behavior, so datetimes and dates may again compare equal, but restore the 0.23.0 behavior in a future release.

To summarize, here's the behavior in 0.22.0, 0.23.0, 0.23.1:

.. code-block:: python

# 0.22.0... Silently coerce the datetime.date
>>> Series(pd.date_range('2017', periods=2)) == datetime.date(2017, 1, 1)
0 True
1 False
dtype: bool

# 0.23.0... Do not coerce the datetime.date
>>> Series(pd.date_range('2017', periods=2)) == datetime.date(2017, 1, 1)
0 False
1 False
dtype: bool

# 0.23.1... Coerce the datetime.date with a warning
>>> Series(pd.date_range('2017', periods=2)) == datetime.date(2017, 1, 1)
/bin/python:1: FutureWarning: Comparing Series of datetimes with 'datetime.date'. Currently, the
'datetime.date' is coerced to a datetime. In the future pandas will
not coerce, and the values not compare equal to the 'datetime.date'.
To retain the current behavior, convert the 'datetime.date' to a
datetime with 'pd.Timestamp'.
#!/bin/python3
0 True
1 False
dtype: bool

In addition, ordering comparisons will raise a ``TypeError`` in the future.

**Other Fixes**

- Reverted the ability of :func:`~DataFrame.to_sql` to perform multivalue
inserts as this caused regression in certain cases (:issue:`21103`).
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30 changes: 30 additions & 0 deletions pandas/core/ops.py
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Expand Up @@ -5,7 +5,10 @@
"""
# necessary to enforce truediv in Python 2.X
from __future__ import division
import datetime
import operator
import textwrap
import warnings

import numpy as np
import pandas as pd
Expand Down Expand Up @@ -1197,8 +1200,35 @@ def wrapper(self, other, axis=None):
if is_datetime64_dtype(self) or is_datetime64tz_dtype(self):
# Dispatch to DatetimeIndex to ensure identical
# Series/Index behavior
if (isinstance(other, datetime.date) and
not isinstance(other, datetime.datetime)):
# https://github.com/pandas-dev/pandas/issues/21152
# Compatibility for difference between Series comparison w/
# datetime and date
msg = (
"Comparing Series of datetimes with 'datetime.date'. "
"Currently, the 'datetime.date' is coerced to a "
"datetime. In the future pandas will not coerce, "
"and {future}. "
"To retain the current behavior, "
"convert the 'datetime.date' to a datetime with "
"'pd.Timestamp'."
)

if op in {operator.lt, operator.le, operator.gt, operator.ge}:
future = "a TypeError will be raised"
else:
future = (
"'the values will not compare equal to the "
"'datetime.date'"
)
msg = '\n'.join(textwrap.wrap(msg.format(future=future)))
warnings.warn(msg, FutureWarning, stacklevel=2)
other = pd.Timestamp(other)

res_values = dispatch_to_index_op(op, self, other,
pd.DatetimeIndex)

return self._constructor(res_values, index=self.index,
name=res_name)

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40 changes: 40 additions & 0 deletions pandas/tests/series/test_arithmetic.py
Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,46 @@ def test_ser_cmp_result_names(self, names, op):


class TestTimestampSeriesComparison(object):
def test_dt64_ser_cmp_date_warning(self):
# https://github.com/pandas-dev/pandas/issues/21359
# Remove this test and enble invalid test below
ser = pd.Series(pd.date_range('20010101', periods=10), name='dates')
date = ser.iloc[0].to_pydatetime().date()

with tm.assert_produces_warning(FutureWarning) as m:
result = ser == date
expected = pd.Series([True] + [False] * 9, name='dates')
tm.assert_series_equal(result, expected)
assert "Comparing Series of datetimes " in str(m[0].message)
assert "will not compare equal" in str(m[0].message)

with tm.assert_produces_warning(FutureWarning) as m:
result = ser != date
tm.assert_series_equal(result, ~expected)
assert "will not compare equal" in str(m[0].message)

with tm.assert_produces_warning(FutureWarning) as m:
result = ser <= date
tm.assert_series_equal(result, expected)
assert "a TypeError will be raised" in str(m[0].message)

with tm.assert_produces_warning(FutureWarning) as m:
result = ser < date
tm.assert_series_equal(result, pd.Series([False] * 10, name='dates'))
assert "a TypeError will be raised" in str(m[0].message)

with tm.assert_produces_warning(FutureWarning) as m:
result = ser >= date
tm.assert_series_equal(result, pd.Series([True] * 10, name='dates'))
assert "a TypeError will be raised" in str(m[0].message)

with tm.assert_produces_warning(FutureWarning) as m:
result = ser > date
tm.assert_series_equal(result, pd.Series([False] + [True] * 9,
name='dates'))
assert "a TypeError will be raised" in str(m[0].message)

@pytest.mark.skip(reason="GH-21359")
def test_dt64ser_cmp_date_invalid(self):
# GH#19800 datetime.date comparison raises to
# match DatetimeIndex/Timestamp. This also matches the behavior
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