Squashed commit of the following:

commit c4b0b97
Author: Tom Augspurger <[email protected]>
Date:   Thu Aug 16 14:36:39 2018 -0500

    Slice based

commit c980035
Author: Tom Augspurger <[email protected]>
Date:   Thu Aug 16 14:20:21 2018 -0500

    Updated

commit b29dfc6
Author: Tom Augspurger <[email protected]>
Date:   Thu Aug 16 10:45:38 2018 -0500

    Support NDFrame.shift with EAs

    Uses take internally.

    Closes pandas-dev#22386

commit b5d81cf
Author: William Ayd <[email protected]>
Date:   Thu Aug 16 03:54:18 2018 -0700

    Bump pytest (pandas-dev#22320)

commit f07a790
Author: jbrockmendel <[email protected]>
Date:   Thu Aug 16 03:46:58 2018 -0700

    Make more of numpy_helper unnecessary (pandas-dev#22344)

commit 7b80d4d
Author: Graham Inggs <[email protected]>
Date:   Thu Aug 16 12:43:02 2018 +0200

    Drop redundant TestLocale (pandas-dev#22349)

commit 6bcfc46
Author: Matthew Roeschke <[email protected]>
Date:   Thu Aug 16 03:32:31 2018 -0700

    Fix failing dateutil test (pandas-dev#22354)

commit 86e8f23
Author: jbrockmendel <[email protected]>
Date:   Thu Aug 16 03:08:09 2018 -0700

    remove last cython: nprofile comments (pandas-dev#22371)

commit 70e6f7c
Author: Joris Van den Bossche <[email protected]>
Date:   Wed Aug 15 18:09:50 2018 +0200

    DOC: edit docstring example to prevent segfault (pandas-dev#21824) (pandas-dev#22368)

Author: TomAugspurger

doc/source/whatsnew/v0.24.0.txt

@@ -462,7 +462,7 @@ ExtensionType Changes
 - Added ``ExtensionDtype._is_numeric`` for controlling whether an extension dtype is considered numeric (:issue:`22290`).
 - The ``ExtensionArray`` constructor, ``_from_sequence`` now take the keyword arg ``copy=False`` (:issue:`21185`)
 - Bug in :meth:`Series.get` for ``Series`` using ``ExtensionArray`` and integer index (:issue:`21257`)
-- :meth:`~Series.shift` now works with extension arrays, rather than raising an AttributeError (:isseu:`22386`)
+- :meth:`~Series.shift` now dispatches to :meth:`ExtensionArray.shift` (:issue:`22386`)
 - :meth:`Series.combine()` works correctly with :class:`~pandas.api.extensions.ExtensionArray` inside of :class:`Series` (:issue:`20825`)
 - :meth:`Series.combine()` with scalar argument now works for any function type (:issue:`21248`)
 - Added ``ExtensionDtype._is_numeric`` for controlling whether an extension dtype is considered numeric.

pandas/core/arrays/base.py

@@ -400,6 +400,36 @@ def dropna(self):
 
         return self[~self.isna()]
 
+    def shift(self, periods=1):
+        # type: (int) -> ExtensionArray
+        """
+        Shift values by desired number.
+
+        Newly introduced missing values are filled with
+        ``self.dtype.na_value``.
+
+        Parameters
+        ----------
+        periods : int, default 1
+            The number of periods to shift. Negative values are allowed
+            for shifting backwards.
+
+        Returns
+        -------
+        shifted : ExtensionArray
+        """
+        if periods == 0:
+            return self.copy()
+        empty = self._from_sequence([self.dtype.na_value] * abs(periods),
+                                    dtype=self.dtype)
+        if periods > 0:
+            a = empty
+            b = self[:-periods]
+        else:
+            a = self[abs(periods):]
+            b = empty
+        return self._concat_same_type([a, b])
+
     def unique(self):
         """Compute the ExtensionArray of unique values.
 

pandas/core/internals/blocks.py

@@ -2074,18 +2074,9 @@ def interpolate(self, method='pad', axis=0, inplace=False, limit=None,
                                  limit=limit),
             placement=self.mgr_locs)
 
-
     def shift(self, periods, axis=0, mgr=None):
-        # type: (int, int, Optional[BlockPlacement]) -> List[ExtensionBlock]
-        indexer = np.roll(np.arange(len(self)), periods)
-
-        if periods > 0:
-            indexer[:periods] = -1
-        else:
-            indexer[periods:] = -1
-
-        new_values = self.values.take(indexer, allow_fill=True)
-        return [self.make_block_same_class(new_values,
+        # type: (int, Optional[BlockPlacement]) -> List[ExtensionBlock]
+        return [self.make_block_same_class(self.values.shift(periods=periods),
                                            placement=self.mgr_locs,
                                            ndim=self.ndim)]
 
@@ -2718,10 +2709,6 @@ def _try_coerce_result(self, result):
 
         return result
 
-    def shift(self, periods, axis=0, mgr=None):
-        return self.make_block_same_class(values=self.values.shift(periods),
-                                          placement=self.mgr_locs)
-
     def to_dense(self):
         # Categorical.get_values returns a DatetimeIndex for datetime
         # categories, so we can't simply use `np.asarray(self.values)` like

pandas/core/sparse/array.py

@@ -749,6 +749,11 @@ def map(self, mapper):
         return type(self)(sp_values, sparse_index=self.sp_index,
                           fill_value=fill_value)
 
+    def shift(self, periods=1):
+        if not self._null_fill_value:
+            return super(SparseArray, self).shift(periods=periods)
+
+
     def get_values(self, fill=None):
         """ return a dense representation """
         # TODO: deprecate for to_dense?

pandas/tests/extension/base/methods.py

@@ -157,9 +157,9 @@ def test_container_shift_negative(self, data, frame, periods, indices):
                 expected,
                 pd.Series([1] * 5, name='B').shift(periods)
             ], axis=1)
-            compare = tm.assert_frame_equal
+            compare = self.assert_frame_equal
         else:
             result = data.shift(periods)
-            compare = tm.assert_series_equal
+            compare = self.assert_series_equal
 
         compare(result, expected)