ENH: Add ignore_index for df.sort_values and series.sort_values (#30402)

Author: charlesdong1991

doc/source/whatsnew/v1.0.0.rst

@@ -207,6 +207,7 @@ Other enhancements
 - The ``partition_cols`` argument in :meth:`DataFrame.to_parquet` now accepts a string (:issue:`27117`)
 - :func:`to_parquet` now appropriately handles the ``schema`` argument for user defined schemas in the pyarrow engine. (:issue: `30270`)
 - DataFrame constructor preserve `ExtensionArray` dtype with `ExtensionArray` (:issue:`11363`)
+- :meth:`DataFrame.sort_values` and :meth:`Series.sort_values` have gained ``ignore_index`` keyword to be able to reset index after sorting (:issue:`30114`)
 
 
 Build Changes

pandas/core/frame.py

@@ -4731,6 +4731,7 @@ def sort_values(
         inplace=False,
         kind="quicksort",
         na_position="last",
+        ignore_index=False,
     ):
         inplace = validate_bool_kwarg(inplace, "inplace")
         axis = self._get_axis_number(axis)
@@ -4764,6 +4765,9 @@ def sort_values(
             indexer, axis=self._get_block_manager_axis(axis), verify=False
         )
 
+        if ignore_index:
+            new_data.axes[1] = ibase.default_index(len(indexer))
+
         if inplace:
             return self._update_inplace(new_data)
         else:

pandas/core/generic.py

@@ -4050,6 +4050,7 @@ def sort_values(
         inplace: bool_t = False,
         kind: str = "quicksort",
         na_position: str = "last",
+        ignore_index: bool_t = False,
     ):
         """
         Sort by the values along either axis.
@@ -4072,6 +4073,10 @@ def sort_values(
         na_position : {'first', 'last'}, default 'last'
              Puts NaNs at the beginning if `first`; `last` puts NaNs at the
              end.
+        ignore_index : bool, default False
+             If True, the resulting axis will be labeled 0, 1, …, n - 1.
+
+             .. versionadded:: 1.0.0
 
         Returns
         -------

pandas/core/series.py

@@ -2698,6 +2698,7 @@ def sort_values(
         inplace=False,
         kind="quicksort",
         na_position="last",
+        ignore_index=False,
     ):
         """
         Sort by the values.
@@ -2720,6 +2721,10 @@ def sort_values(
         na_position : {'first' or 'last'}, default 'last'
             Argument 'first' puts NaNs at the beginning, 'last' puts NaNs at
             the end.
+        ignore_index : bool, default False
+             If True, the resulting axis will be labeled 0, 1, …, n - 1.
+
+             .. versionadded:: 1.0.0
 
         Returns
         -------
@@ -2825,7 +2830,7 @@ def _try_kind_sort(arr):
                 return arr.argsort(kind="quicksort")
 
         arr = self._values
-        sortedIdx = np.empty(len(self), dtype=np.int32)
+        sorted_index = np.empty(len(self), dtype=np.int32)
 
         bad = isna(arr)
 
@@ -2849,16 +2854,19 @@ def _try_kind_sort(arr):
 
         if na_position == "last":
             n = good.sum()
-            sortedIdx[:n] = idx[good][argsorted]
-            sortedIdx[n:] = idx[bad]
+            sorted_index[:n] = idx[good][argsorted]
+            sorted_index[n:] = idx[bad]
         elif na_position == "first":
             n = bad.sum()
-            sortedIdx[n:] = idx[good][argsorted]
-            sortedIdx[:n] = idx[bad]
+            sorted_index[n:] = idx[good][argsorted]
+            sorted_index[:n] = idx[bad]
         else:
             raise ValueError(f"invalid na_position: {na_position}")
 
-        result = self._constructor(arr[sortedIdx], index=self.index[sortedIdx])
+        result = self._constructor(arr[sorted_index], index=self.index[sorted_index])
+
+        if ignore_index:
+            result.index = ibase.default_index(len(sorted_index))
 
         if inplace:
             self._update_inplace(result)

pandas/tests/frame/methods/test_sort_values.py

@@ -460,3 +460,45 @@ def test_sort_values_na_position_with_categories_raises(self):
 
         with pytest.raises(ValueError):
             df.sort_values(by="c", ascending=False, na_position="bad_position")
+
+    @pytest.mark.parametrize(
+        "original_dict, sorted_dict, ignore_index, output_index",
+        [
+            ({"A": [1, 2, 3]}, {"A": [3, 2, 1]}, True, [0, 1, 2]),
+            ({"A": [1, 2, 3]}, {"A": [3, 2, 1]}, False, [2, 1, 0]),
+            (
+                {"A": [1, 2, 3], "B": [2, 3, 4]},
+                {"A": [3, 2, 1], "B": [4, 3, 2]},
+                True,
+                [0, 1, 2],
+            ),
+            (
+                {"A": [1, 2, 3], "B": [2, 3, 4]},
+                {"A": [3, 2, 1], "B": [4, 3, 2]},
+                False,
+                [2, 1, 0],
+            ),
+        ],
+    )
+    def test_sort_values_ignore_index(
+        self, original_dict, sorted_dict, ignore_index, output_index
+    ):
+        # GH 30114
+        df = DataFrame(original_dict)
+        expected = DataFrame(sorted_dict, index=output_index)
+
+        # Test when inplace is False
+        sorted_df = df.sort_values("A", ascending=False, ignore_index=ignore_index)
+        tm.assert_frame_equal(sorted_df, expected)
+
+        tm.assert_frame_equal(df, DataFrame(original_dict))
+
+        # Test when inplace is True
+        copied_df = df.copy()
+
+        copied_df.sort_values(
+            "A", ascending=False, ignore_index=ignore_index, inplace=True
+        )
+        tm.assert_frame_equal(copied_df, expected)
+
+        tm.assert_frame_equal(df, DataFrame(original_dict))

pandas/tests/series/methods/test_sort_values.py

@@ -156,3 +156,30 @@ def test_sort_values_categorical(self):
         result = df.sort_values(by=["grade", "id"])
         expected = df.iloc[[2, 1, 5, 4, 3, 0]]
         tm.assert_frame_equal(result, expected)
+
+    @pytest.mark.parametrize(
+        "original_list, sorted_list, ignore_index, output_index",
+        [
+            ([2, 3, 6, 1], [6, 3, 2, 1], True, [0, 1, 2, 3]),
+            ([2, 3, 6, 1], [6, 3, 2, 1], False, [2, 1, 0, 3]),
+        ],
+    )
+    def test_sort_values_ignore_index(
+        self, original_list, sorted_list, ignore_index, output_index
+    ):
+        # GH 30114
+        sr = Series(original_list)
+        expected = Series(sorted_list, index=output_index)
+
+        # Test when inplace is False
+        sorted_sr = sr.sort_values(ascending=False, ignore_index=ignore_index)
+        tm.assert_series_equal(sorted_sr, expected)
+
+        tm.assert_series_equal(sr, Series(original_list))
+
+        # Test when inplace is True
+        copied_sr = sr.copy()
+        copied_sr.sort_values(ascending=False, ignore_index=ignore_index, inplace=True)
+        tm.assert_series_equal(copied_sr, expected)
+
+        tm.assert_series_equal(sr, Series(original_list))