Implement Series.swapaxes

databricks/koalas/frame.py

@@ -6448,14 +6448,12 @@ def swaplevel(self, i=-2, j=-1, axis=0) -> "DataFrame":
 
         return DataFrame(internal)
 
-    def swapaxes(
-        self, i: Union[str, int] = 0, j: Union[str, int] = 1, copy: bool = True
-    ) -> "DataFrame":
+    def swapaxes(self, i: Union[str, int], j: Union[str, int], copy: bool = True) -> "DataFrame":
         """
         Interchange axes and swap values axes appropriately.
 
-        .. note:: This method is based on an expensive operation due to the nature
-            of big data. Internally it needs to generate each row for each value, and
+        .. note:: This method, if applied to a DataFrame, is based on an expensive operation due to
+            the nature of big data. Internally it needs to generate each row for each value, and
             then group twice - it is a huge operation. To prevent misusage, this method
             has the 'compute.max_rows' default limit of input length, and raises a ValueError.
 
@@ -6471,8 +6469,9 @@ def swapaxes(
 
         Parameters
         ----------
-        i: {0 or 'index', 1 or 'columns'}, default 0. The axis to swap.
-        j: {0 or 'index', 1 or 'columns'}, default 1. The axis to swap.
+        i: {0 or 'index', 1 or 'columns'}. The axis to swap.
+        j: {0 or 'index', 1 or 'columns'}. The axis to swap.
+        copy : bool, default True.
 
         Returns
         -------
@@ -6488,11 +6487,6 @@ def swapaxes(
         x  1  2  3
         y  4  5  6
         z  7  8  9
-        >>> kdf.swapaxes()
-           x  y  z
-        a  1  4  7
-        b  2  5  8
-        c  3  6  9
         >>> kdf.swapaxes(i=1, j=0)
            x  y  z
         a  1  4  7
@@ -6505,10 +6499,11 @@ def swapaxes(
         z  7  8  9
         """
         assert copy is True
+
         i = validate_axis(i)
         j = validate_axis(j)
 
-        return self if i == j else self.transpose()
+        return self.copy() if i == j else self.transpose()
 
     def _swaplevel_columns(self, i, j) -> InternalFrame:
         assert isinstance(self.columns, pd.MultiIndex)

databricks/koalas/missing/series.py

@@ -55,7 +55,6 @@ class MissingPandasLikeSeries(object):
     sem = _unsupported_function("sem")
     set_axis = _unsupported_function("set_axis")
     slice_shift = _unsupported_function("slice_shift")
-    swapaxes = _unsupported_function("swapaxes")
     to_hdf = _unsupported_function("to_hdf")
     to_period = _unsupported_function("to_period")
     to_sql = _unsupported_function("to_sql")

databricks/koalas/series.py

@@ -2486,6 +2486,46 @@ def swaplevel(self, i=-2, j=-1, copy: bool = True) -> "Series":
 
         return first_series(self.to_frame().swaplevel(i, j, axis=0)).rename(self.name)
 
+    def swapaxes(self, i: Union[str, int], j: Union[str, int], copy: bool = True) -> "Series":
+        """
+        Interchange axes and swap values axes appropriately.
+
+        Parameters
+        ----------
+        i: {0 or 'index', 1 or 'columns'}. The axis to swap.
+        j: {0 or 'index', 1 or 'columns'}. The axis to swap.
+        copy : bool, default True.
+
+        Returns
+        -------
+        Series
+
+        Examples
+        --------
+        On a Series:
+
+        >>> kser = ks.Series([1, 2, 3], index=["x", "y", "z"])
+        >>> kser
+        x    1
+        y    2
+        z    3
+        dtype: int64
+        >>>
+        >>> kser.swapaxes(0, 0)
+        x    1
+        y    2
+        z    3
+        dtype: int64
+        """
+        assert copy is True
+
+        i = validate_axis(i)
+        j = validate_axis(j)
+        if not i == j == 0:
+            raise ValueError("Axis must be 0 for Series")
+
+        return self.copy()
+
     def add_prefix(self, prefix) -> "Series":
         """
         Prefix labels with string `prefix`.

databricks/koalas/tests/test_dataframe.py

@@ -1453,6 +1453,7 @@ def test_swapaxes(self):
 
         self.assertRaises(AssertionError, lambda: kdf.swapaxes(0, 1, copy=False))
         self.assertRaises(ValueError, lambda: kdf.swapaxes(0, -1))
+        self.assertRaises(TypeError, lambda: kdf.swapaxes())
 
     def test_nlargest(self):
         pdf = pd.DataFrame(

databricks/koalas/tests/test_series.py

@@ -1853,6 +1853,19 @@ def test_swaplevel(self):
         self.assertRaises(KeyError, lambda: kser.swaplevel("not_number", "color"))
         self.assertRaises(AssertionError, lambda: kser.swaplevel(copy=False))
 
+    def test_swapaxes(self):
+        pser = pd.Series([1, 2, 3], index=["x", "y", "z"], name="ser")
+        kser = ks.from_pandas(pser)
+
+        self.assert_eq(kser.swapaxes(0, 0), pser.swapaxes(0, 0))
+        self.assert_eq(kser.swapaxes("index", "index"), pser.swapaxes("index", "index"))
+        self.assert_eq((kser + 1).swapaxes(0, 0), (pser + 1).swapaxes(0, 0))
+
+        self.assertRaises(AssertionError, lambda: kser.swapaxes(0, 1, copy=False))
+        self.assertRaises(ValueError, lambda: kser.swapaxes(0, 1))
+        self.assertRaises(ValueError, lambda: kser.swapaxes("index", "columns"))
+        self.assertRaises(TypeError, lambda: kser.swapaxes())
+
     def test_div_zero_and_nan(self):
         pser = pd.Series([100, None, -300, None, 500, -700, np.inf, -np.inf], name="Koalas")
         kser = ks.from_pandas(pser)

docs/source/reference/series.rst

@@ -176,6 +176,7 @@ Reindexing / Selection / Label manipulation
    Series.reset_index
    Series.sample
    Series.swaplevel
+   Series.swapaxes
    Series.take
    Series.tail
    Series.where