Initial commit

python/cudf/cudf/_lib/pylibcudf/lists.pxd

@@ -25,4 +25,4 @@ cpdef Column contains_nulls(Column)
 
 cpdef Column index_of(Column, ColumnOrScalar, bool)
 
-cpdef Column segmented_gather(Column, Column, bool)
+cpdef Column segmented_gather(Column, Column)

python/cudf/cudf/_lib/pylibcudf/lists.pyx

@@ -9,6 +9,7 @@ from cudf._lib.pylibcudf.libcudf.column.column cimport column
 from cudf._lib.pylibcudf.libcudf.lists cimport (
     contains as cpp_contains,
     explode as cpp_explode,
+    gather as cpp_gather,
 )
 from cudf._lib.pylibcudf.libcudf.lists.combine cimport (
     concatenate_list_elements as cpp_concatenate_list_elements,
@@ -208,7 +209,32 @@ cpdef Column index_of(Column input, ColumnOrScalar search_key, bool find_first_o
     return Column.from_libcudf(move(c_result))
 
 
-cpdef Column segmented_gather(Column input, Column gather_map_list, bool check_bounds):
-    """column with elements in list of rows gathered based on gather_map_list
+cpdef Column segmented_gather(Column input, Column gather_map_list):
+    """Create a column with elements gathered based on the indices in gather_map_list
+
+    For details, see :cpp:func:`segmented_gather`.
+
+    Parameters
+    ----------
+    input : Column
+        The input column.
+    gather_map_list : Column
+        The indices of the lists column to gather.
+
+    Returns
+    -------
+    Column
+        A new Column with elements in list of rows
+        gathered based on gather_map_list
     """
-    pass
+
+    cdef unique_ptr[column] c_result
+    cdef ListColumnView list_view1 = input.list_view()
+    cdef ListColumnView list_view2 = gather_map_list.list_view()
+
+    with nogil:
+        c_result = move(cpp_gather.segmented_gather(
+            list_view1.view(),
+            list_view2.view(),
+        ))
+    return Column.from_libcudf(move(c_result))

python/cudf/cudf/pylibcudf_tests/test_lists.py

@@ -134,3 +134,17 @@ def test_index_of_list_column(test_data, column):
     expect = pa.array(column[1], type=pa.int32())
 
     assert_column_eq(expect, res)
+
+
+def test_segmented_gather(test_data):
+    list_column1 = test_data[0][0]
+    list_column2 = test_data[0][1]
+
+    plc_column1 = plc.interop.from_arrow(pa.array(list_column1))
+    plc_column2 = plc.interop.from_arrow(pa.array(list_column2))
+
+    res = plc.lists.segmented_gather(plc_column2, plc_column1)
+
+    expect = pa.array([[8, 9], [14], [0], [0, 0]])
+
+    assert_column_eq(expect, res)