Updated

Author: TomAugspurger

doc/source/whatsnew/v0.24.0.txt

@@ -444,7 +444,7 @@ ExtensionType Changes
   the ``ExtensionDtype`` has gained the method ``construct_array_type`` (:issue:`21185`)
 - 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`)
 -

pandas/core/arrays/base.py

@@ -400,6 +400,33 @@ 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
+        """
+        indexer = np.roll(np.arange(len(self)), periods)
+
+        if periods > 0:
+            indexer[:periods] = -1
+        else:
+            indexer[periods:] = -1
+
+        return self.take(indexer, allow_fill=True)
+
     def unique(self):
         """Compute the ExtensionArray of unique values.
 

pandas/core/internals/blocks.py

@@ -2062,23 +2062,11 @@ def interpolate(self, method='pad', axis=0, inplace=False, limit=None,
             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)]
 
-    @property
-    def _ftype(self):
-        return getattr(self.values, '_pandas_ftype', Block._ftype)
-
 
 class NumericBlock(Block):
     __slots__ = ()
@@ -2702,10 +2690,6 @@ 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/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)