ENH: add ignore index to DataFrame / Series.sample (#42168)

Author: mzeitlin11

doc/source/whatsnew/v1.3.0.rst

@@ -278,6 +278,7 @@ Other enhancements
 - Improved error message in ``corr`` and ``cov`` methods on :class:`.Rolling`, :class:`.Expanding`, and :class:`.ExponentialMovingWindow` when ``other`` is not a :class:`DataFrame` or :class:`Series` (:issue:`41741`)
 - :meth:`Series.between` can now accept ``left`` or ``right`` as arguments to ``inclusive`` to include only the left or right boundary (:issue:`40245`)
 - :meth:`DataFrame.explode` now supports exploding multiple columns. Its ``column`` argument now also accepts a list of str or tuples for exploding on multiple columns at the same time (:issue:`39240`)
+- :meth:`DataFrame.sample` now accepts the ``ignore_index`` argument to reset the index after sampling, similar to :meth:`DataFrame.drop_duplicates` and :meth:`DataFrame.sort_values` (:issue:`38581`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/generic.py

@@ -5144,11 +5144,12 @@ def tail(self: FrameOrSeries, n: int = 5) -> FrameOrSeries:
     def sample(
         self: FrameOrSeries,
         n=None,
-        frac=None,
-        replace=False,
+        frac: float | None = None,
+        replace: bool_t = False,
         weights=None,
         random_state: RandomState | None = None,
-        axis=None,
+        axis: Axis | None = None,
+        ignore_index: bool_t = False,
     ) -> FrameOrSeries:
         """
         Return a random sample of items from an axis of object.
@@ -5189,6 +5190,10 @@ def sample(
         axis : {0 or ‘index’, 1 or ‘columns’, None}, default None
             Axis to sample. Accepts axis number or name. Default is stat axis
             for given data type (0 for Series and DataFrames).
+        ignore_index : bool, default False
+            If True, the resulting index will be labeled 0, 1, …, n - 1.
+
+            .. versionadded:: 1.3.0
 
         Returns
         -------
@@ -5350,7 +5355,11 @@ def sample(
             )
 
         locs = rs.choice(axis_length, size=n, replace=replace, p=weights)
-        return self.take(locs, axis=axis)
+        result = self.take(locs, axis=axis)
+        if ignore_index:
+            result.index = ibase.default_index(len(result))
+
+        return result
 
     @final
     @doc(klass=_shared_doc_kwargs["klass"])

pandas/tests/frame/methods/test_sample.py

@@ -5,6 +5,7 @@
 
 from pandas import (
     DataFrame,
+    Index,
     Series,
 )
 import pandas._testing as tm
@@ -326,3 +327,12 @@ def test_sample_is_copy(self):
 
         with tm.assert_produces_warning(None):
             df2["d"] = 1
+
+    def test_sample_ignore_index(self):
+        # GH 38581
+        df = DataFrame(
+            {"col1": range(10, 20), "col2": range(20, 30), "colString": ["a"] * 10}
+        )
+        result = df.sample(3, ignore_index=True)
+        expected_index = Index([0, 1, 2])
+        tm.assert_index_equal(result.index, expected_index)