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Make pd.Period immutable #17239

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Merged
merged 15 commits into from
Aug 24, 2017
Merged

Make pd.Period immutable #17239

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89cf9d6
Make Period ordinal and freq readonly
jbrockmendel Aug 12, 2017
e6ca02c
Tests for Period immutability
jbrockmendel Aug 12, 2017
8912283
Trim whitespace
jbrockmendel Aug 13, 2017
d33922f
flake8 whitespace fixup
jbrockmendel Aug 13, 2017
b86a7b9
Add note in whatsnew; address reviewer requests
jbrockmendel Aug 19, 2017
1c6f197
flake8 whitespace fixup
jbrockmendel Aug 20, 2017
08a218c
Merge branch 'master' into period_immutable
jbrockmendel Aug 20, 2017
2642366
More brevity
jbrockmendel Aug 20, 2017
6c461eb
Merge branch 'period_immutable' of https://github.com/jbrockmendel/pa…
jbrockmendel Aug 20, 2017
0e62865
Merge branch 'master' into period_immutable
jbrockmendel Aug 22, 2017
cd687bf
Remove message per reviewer suggestion
jbrockmendel Aug 23, 2017
dc2111c
unwrap line per reviewer request
jbrockmendel Aug 23, 2017
1e92344
Merge branch 'period_immutable' of https://github.com/jbrockmendel/pa…
jbrockmendel Aug 23, 2017
19567c8
Try to guess what jreback wants
jbrockmendel Aug 23, 2017
f739f8f
move whatsnew to correct location
jreback Aug 24, 2017
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2 changes: 2 additions & 0 deletions doc/source/whatsnew/v0.21.0.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -137,6 +137,8 @@ Other Enhancements
Backwards incompatible API changes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

:class:`Period` will now raise an ``AttributeError`` when a user tries to assign a new value to the `ordinal` or `freq` attributes (:issue:`17116`).
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@jreback jreback Aug 23, 2017

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no what I meant was remove this as a sub-section and just add it as a single like in other breaking changes.
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@jbrockmendel jbrockmendel Aug 23, 2017

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All the other breaking changes have a subsection like:

.. _whatsnew_0210.api_breaking.pandas_eval: Improved error handling during item assignment in pd.eval ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I'll keep pushing guesses until the Infinite Monkeys Theorem kicks in.
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@jorisvandenbossche jorisvandenbossche Aug 24, 2017

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Still not fully what he meant :-)

The "Backwards incompatible API changes" section starts with subsections for things that we think are important enough to explain in more than a single line, and at the end there is section "other API changes" with a bunch of single entries:

https://github.com/jbrockmendel/pandas/blob/19567c8f0de212dec15e17dc918e6eada6a8c354/doc/source/whatsnew/v0.21.0.txt#L280-L295

So you can put it there.


.. _whatsnew_0210.api_breaking.deps:

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17 changes: 11 additions & 6 deletions pandas/_libs/period.pyx
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Expand Up @@ -29,7 +29,9 @@ from datetime cimport (
PANDAS_FR_ns,
INT32_MIN)


cimport util, lib

from lib cimport is_null_datetimelike, is_period
from pandas._libs import tslib, lib
from pandas._libs.tslib import (Timedelta, Timestamp, iNaT,
Expand Down Expand Up @@ -668,13 +670,17 @@ class IncompatibleFrequency(ValueError):

cdef class _Period(object):

cdef public:
cdef readonly:
int64_t ordinal
object freq

_comparables = ['name', 'freqstr']
_typ = 'period'

def __cinit__(self, ordinal, freq):
self.ordinal = ordinal
self.freq = freq

@classmethod
def _maybe_convert_freq(cls, object freq):

Expand All @@ -698,9 +704,8 @@ cdef class _Period(object):
if ordinal == iNaT:
return NaT
else:
self = _Period.__new__(cls)
self.ordinal = ordinal
self.freq = cls._maybe_convert_freq(freq)
freq = cls._maybe_convert_freq(freq)
self = _Period.__new__(cls, ordinal, freq)
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@max-sixty max-sixty Aug 19, 2017

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Should this be self = cls.__new__...?
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@jbrockmendel jbrockmendel Aug 19, 2017

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I don't think so. cls._from_ordinal gets called at the end of Period.__new__, so I expect it explicitly needs to be _Period.
return self

def __richcmp__(self, other, op):
Expand Down Expand Up @@ -752,7 +757,7 @@ cdef class _Period(object):
def __add__(self, other):
if isinstance(self, Period):
if isinstance(other, (timedelta, np.timedelta64,
offsets.Tick, offsets.DateOffset,
offsets.DateOffset,
Timedelta)):
return self._add_delta(other)
elif other is NaT:
Expand All @@ -770,7 +775,7 @@ cdef class _Period(object):
def __sub__(self, other):
if isinstance(self, Period):
if isinstance(other, (timedelta, np.timedelta64,
offsets.Tick, offsets.DateOffset,
offsets.DateOffset,
Timedelta)):
neg_other = -other
return self + neg_other
Expand Down
11 changes: 11 additions & 0 deletions pandas/tests/scalar/test_period.py
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Expand Up @@ -1406,3 +1406,14 @@ def test_period_ops_offset(self):

with tm.assert_raises_regex(period.IncompatibleFrequency, msg):
p - offsets.Hour(2)


def test_period_immutable():
# see gh-17116
per = pd.Period('2014Q1')
with pytest.raises(AttributeError):
per.ordinal = 14

freq = per.freq
with pytest.raises(AttributeError):
per.freq = 2 * freq