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err#8038: Index.shift() gives confusing error message when no Datetim… #11211

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err#8038 :add fix, note and test 
err#8038 : add fix, note and test

err#8038 : add fix, note and test

fix added with tests

modification

Index.shift() gives confusing error message when no DatetimeIndex

test, fix note

change tests

add issue number

test change

test change

add tests

add test
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Hamed Saljooghinejad committed Nov 18, 2015
commit 58769ec1cfeeb015ab25c3581401c655aa5ee30f
2 changes: 1 addition & 1 deletion doc/source/whatsnew/v0.17.1.txt
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Expand Up @@ -98,7 +98,7 @@ Enhancements

API changes
~~~~~~~~~~~

- raise ``NotImplementedError`` in ``Index.shift`` for non-supported index types (:issue:`8083`)
- min and max reductions on ``datetime64`` and ``timedelta64`` dtyped series now
result in ``NaT`` and not ``nan`` (:issue:`11245`).
- Regression from 0.16.2 for output formatting of long floats/nan, restored in (:issue:`11302`)
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7 changes: 1 addition & 6 deletions pandas/core/index.py
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Expand Up @@ -1461,12 +1461,7 @@ def shift(self, periods=1, freq=None):
-------
shifted : Index
"""
if periods == 0:
# OK because immutable
return self

offset = periods * freq
return Index([idx + offset for idx in self], name=self.name)
raise NotImplementedError("Not supported for type %s" % type(self).__name__)

def argsort(self, *args, **kwargs):
"""
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58 changes: 58 additions & 0 deletions pandas/tests/test_index.py
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Expand Up @@ -53,6 +53,13 @@ def test_pickle_compat_construction(self):
# need an object to create with
self.assertRaises(TypeError, self._holder)

def test_shift_index(self):
# err8083 test the base class for shift
idx = self.create_index()
self.assertRaises(NotImplementedError, idx.shift, 1)

self.assertRaises(NotImplementedError, idx.shift, 1, 2)

def test_numeric_compat(self):

idx = self.create_index()
Expand Down Expand Up @@ -3425,6 +3432,32 @@ def setUp(self):
def create_index(self):
return date_range('20130101', periods=5)

def test_shift(self):
# test shift for datetimeIndex and non datetimeIndex
# err8083

drange = self.create_index()
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@jreback jreback Nov 16, 2015

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this is ONLY true for DatetimeIndex. Need separate expectation for TimedeltaIndex/PeriodIndex (IOW separate methods).

result = drange.shift(1)
expected = DatetimeIndex(['2013-01-02', '2013-01-03', '2013-01-04', '2013-01-05',
'2013-01-06'], freq='D')
self.assert_index_equal(result, expected)

result = drange.shift(0)
expected = DatetimeIndex(['2013-01-01', '2013-01-02', '2013-01-03', '2013-01-04',
'2013-01-05'], freq='D')
self.assert_index_equal(result, expected)

result = drange.shift(-1)
expected = DatetimeIndex(['2012-12-31','2013-01-01', '2013-01-02', '2013-01-03', '2013-01-04'],
freq='D')
self.assert_index_equal(result, expected)

result = drange.shift(3, freq='2D')
expected = DatetimeIndex(['2013-01-07', '2013-01-08', '2013-01-09', '2013-01-10',
'2013-01-11'],freq='D')
self.assert_index_equal(result, expected)


def test_construction_with_alt(self):

i = pd.date_range('20130101',periods=5,freq='H',tz='US/Eastern')
Expand Down Expand Up @@ -3688,6 +3721,16 @@ def setUp(self):
def create_index(self):
return period_range('20130101', periods=5, freq='D')

def test_shift(self):
# test shift for PeriodIndex
# err8083

drange = self.create_index()
result = drange.shift(1)
expected = PeriodIndex(['2013-01-02', '2013-01-03', '2013-01-04', '2013-01-05',
'2013-01-06'], freq='D')
self.assert_index_equal(result, expected)

def test_pickle_compat_construction(self):
pass

Expand Down Expand Up @@ -3784,6 +3827,21 @@ def setUp(self):
def create_index(self):
return pd.to_timedelta(range(5), unit='d') + pd.offsets.Hour(1)

def test_shift(self):
# test shift for TimedeltaIndex
# err8083

drange = self.create_index()
result = drange.shift(1)
expected = TimedeltaIndex(['1 days 01:00:00', '2 days 01:00:00', '3 days 01:00:00',
'4 days 01:00:00', '5 days 01:00:00'],freq='D')
self.assert_index_equal(result, expected)

result = drange.shift(3, freq='2D')
expected = TimedeltaIndex(['2 days 01:00:00', '3 days 01:00:00', '4 days 01:00:00',
'5 days 01:00:00', '6 days 01:00:00'],freq='D')
self.assert_index_equal(result, expected)

def test_get_loc(self):
idx = pd.to_timedelta(['0 days', '1 days', '2 days'])

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5 changes: 3 additions & 2 deletions pandas/tseries/base.py
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Expand Up @@ -516,9 +516,10 @@ def shift(self, n, freq=None):
if freq is not None and freq != self.freq:
if isinstance(freq, compat.string_types):
freq = frequencies.to_offset(freq)
result = Index.shift(self, n, freq)
offset = n * freq
result = self + offset

if hasattr(self,'tz'):
if hasattr(self, 'tz'):
result.tz = self.tz

return result
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