[GitHub] [beam] yeandy commented on a change in pull request #17026: [BEAM-13948] Add unstack(), a non-deferred column operation on categorical columns

[GitBox <gi...@apache.org>]

yeandy commented on a change in pull request #17026:
URL: https://github.com/apache/beam/pull/17026#discussion_r820759175



##########
File path: sdks/python/apache_beam/dataframe/frames_test.py
##########
@@ -2468,6 +2468,112 @@ def test_split_pat_is_regex(self):
     self.assert_frame_data_equivalent(
         result, s.str.split(r"\.jpg", regex=True, expand=False))
 
+  def test_unstack_pandas_series_not_multiindex(self):
+    # Pandas should throw a ValueError if performing unstack
+    # on a Series without MultiIndex
+    s = pd.Series([1, 2, 3, 4], index=['one', 'two', 'three', 'four'])
+    with self.assertRaisesRegex(ValueError,
+                                r"index must be a MultiIndex to unstack"):
+      self._evaluate(lambda s: s.unstack(), s)
+
+  def test_unstack_non_categorical_index(self):
+    index = pd.MultiIndex.from_tuples([('one', 'a'), ('one', 'b'), ('two', 'a'),
+                                       ('two', 'b')])
+    index = index.set_levels(
+        index.levels[0].astype(pd.CategoricalDtype(['one', 'two'])), level=0)
+    s = pd.Series(np.arange(1.0, 5.0), index=index)
+    with self.assertRaisesRegex(
+        frame_base.WontImplementError,
+        r"unstack\(\) is only supported on DataFrames if"):
+      self._evaluate(lambda s: s.unstack(level=-1), s)
+
+  def _unstack_get_categorical_index(self):
+    index = pd.MultiIndex.from_tuples([('one', 'a'), ('one', 'b'), ('two', 'a'),
+                                       ('two', 'b')])
+    index = index.set_levels(
+        index.levels[0].astype(pd.CategoricalDtype(['one', 'two'])), level=0)
+    index = index.set_levels(
+        index.levels[1].astype(pd.CategoricalDtype(['a', 'b'])), level=1)
+    return index
+
+  def test_unstack_pandas_example1(self):
+    index = self._unstack_get_categorical_index()
+    s = pd.Series(np.arange(1.0, 5.0), index=index)
+    result = self._evaluate(lambda s: s.unstack(level=-1), s)
+    self.assert_frame_data_equivalent(result, s.unstack(level=-1))
+
+  def test_unstack_pandas_example2(self):
+    index = self._unstack_get_categorical_index()
+    s = pd.Series(np.arange(1.0, 5.0), index=index)
+    result = self._evaluate(lambda s: s.unstack(level=0), s)
+    self.assert_frame_data_equivalent(result, s.unstack(level=0))
+
+  def test_unstack_pandas_example3(self):
+    index = self._unstack_get_categorical_index()
+    s = pd.Series(np.arange(1.0, 5.0), index=index)
+    result = self._evaluate(lambda s: s.unstack(level=0).unstack(), s)
+    self.assert_frame_data_equivalent(result, s.unstack(level=0).unstack())
+
+  @unittest.skipIf(

Review comment:
       Doesn't work with Python 3.7 (pandas < 1.4) as the dtype of the boolean-casted index column is `object`, not `BooleanDtype`




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