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

Author: Hamed Saljooghinejad

doc/source/whatsnew/v0.17.1.txt

@@ -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`)

pandas/core/index.py

@@ -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):
         """

pandas/tests/test_index.py

@@ -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()
@@ -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()
+        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')
@@ -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
 
@@ -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'])
 

pandas/tseries/base.py

@@ -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