Backport PR #42148 on branch 1.3.x (DOC: share swaplevel docstring between DataFrame and Series (#42120))

pandas/core/frame.py

@@ -6744,23 +6744,16 @@ def nsmallest(self, n, columns, keep: str = "first") -> DataFrame:
             self, n=n, keep=keep, columns=columns
         ).nsmallest()
 
-    def swaplevel(self, i: Axis = -2, j: Axis = -1, axis: Axis = 0) -> DataFrame:
-        """
-        Swap levels i and j in a MultiIndex on a particular axis.
-
-        Parameters
-        ----------
-        i, j : int or str
-            Levels of the indices to be swapped. Can pass level name as string.
-        axis : {0 or 'index', 1 or 'columns'}, default 0
+    @doc(
+        Series.swaplevel,
+        klass=_shared_doc_kwargs["klass"],
+        extra_params=dedent(
+            """axis : {0 or 'index', 1 or 'columns'}, default 0
             The axis to swap levels on. 0 or 'index' for row-wise, 1 or
-            'columns' for column-wise.
-
-        Returns
-        -------
-        DataFrame
-
-        Examples
+            'columns' for column-wise."""
+        ),
+        examples=dedent(
+            """Examples
         --------
         >>> df = pd.DataFrame(
         ...     {"Grade": ["A", "B", "A", "C"]},
@@ -6809,8 +6802,10 @@ def swaplevel(self, i: Axis = -2, j: Axis = -1, axis: Axis = 0) -> DataFrame:
         History     Final exam  January         A
         Geography   Final exam  February        B
         History     Coursework  March           A
-        Geography   Coursework  April           C
-        """
+        Geography   Coursework  April           C"""
+        ),
+    )
+    def swaplevel(self, i: Axis = -2, j: Axis = -1, axis: Axis = 0) -> DataFrame:
         result = self.copy()
 
         axis = self._get_axis_number(axis)

pandas/core/series.py

@@ -3863,6 +3863,65 @@ def nsmallest(self, n: int = 5, keep: str = "first") -> Series:
         """
         return algorithms.SelectNSeries(self, n=n, keep=keep).nsmallest()
 
+    @doc(
+        klass=_shared_doc_kwargs["klass"],
+        extra_params=dedent(
+            """copy : bool, default True
+            Whether to copy underlying data."""
+        ),
+        examples=dedent(
+            """Examples
+        --------
+        >>> s = pd.Series(
+        ...     ["A", "B", "A", "C"],
+        ...     index=[
+        ...         ["Final exam", "Final exam", "Coursework", "Coursework"],
+        ...         ["History", "Geography", "History", "Geography"],
+        ...         ["January", "February", "March", "April"],
+        ...     ],
+        ... )
+        >>> s
+        Final exam  History     January      A
+                    Geography   February     B
+        Coursework  History     March        A
+                    Geography   April        C
+        dtype: object
+
+        In the following example, we will swap the levels of the indices.
+        Here, we will swap the levels column-wise, but levels can be swapped row-wise
+        in a similar manner. Note that column-wise is the default behaviour.
+        By not supplying any arguments for i and j, we swap the last and second to
+        last indices.
+
+        >>> s.swaplevel()
+        Final exam  January     History         A
+                    February    Geography       B
+        Coursework  March       History         A
+                    April       Geography       C
+        dtype: object
+
+        By supplying one argument, we can choose which index to swap the last
+        index with. We can for example swap the first index with the last one as
+        follows.
+
+        >>> s.swaplevel(0)
+        January     History     Final exam      A
+        February    Geography   Final exam      B
+        March       History     Coursework      A
+        April       Geography   Coursework      C
+        dtype: object
+
+        We can also define explicitly which indices we want to swap by supplying values
+        for both i and j. Here, we for example swap the first and second indices.
+
+        >>> s.swaplevel(0, 1)
+        History     Final exam  January         A
+        Geography   Final exam  February        B
+        History     Coursework  March           A
+        Geography   Coursework  April           C
+        dtype: object"""
+        ),
+    )
     def swaplevel(self, i=-2, j=-1, copy=True) -> Series:
         """
         Swap levels i and j in a :class:`MultiIndex`.
@@ -3871,15 +3930,16 @@ def swaplevel(self, i=-2, j=-1, copy=True) -> Series:
 
         Parameters
         ----------
-        i, j : int, str
-            Level of the indices to be swapped. Can pass level name as string.
-        copy : bool, default True
-            Whether to copy underlying data.
+        i, j : int or str
+            Levels of the indices to be swapped. Can pass level name as string.
+        {extra_params}
 
         Returns
         -------
-        Series
-            Series with levels swapped in MultiIndex.
+        {klass}
+            {klass} with levels swapped in MultiIndex.
+
+        {examples}
         """
         assert isinstance(self.index, MultiIndex)
         new_index = self.index.swaplevel(i, j)