Centralize function for generating a list vector of scalars

python/cudf/cudf/_lib/pylibcudf/copying.pyx

@@ -32,6 +32,21 @@ from .table cimport Table
 ctypedef const scalar constscalar
 
 
+cdef vector[reference_wrapper[const scalar]] _make_scalar_vector(list source):
+    """Make a vector of reference_wrapper[const scalar] from a list of scalars."""
+    if not isinstance(source, list) or not isinstance(source[0], Scalar):
+        raise ValueError("source must be a list[Scalar]")
+
+    cdef vector[reference_wrapper[const scalar]] c_scalars
+    c_scalars.reserve(len(source))
+    cdef Scalar slr
+    for slr in source:
+        c_scalars.push_back(
+            reference_wrapper[constscalar](dereference(slr.c_obj))
+        )
+    return c_scalars
+
+
 # TODO: Is it OK to reference the corresponding libcudf algorithm in the
 # documentation? Otherwise there's a lot of room for duplication.
 cpdef Table gather(
@@ -98,24 +113,12 @@ cpdef Table table_scatter(Table source, Column scatter_map, Table target_table):
     return Table.from_libcudf(move(c_result))
 
 
-cdef _check_is_list_of_scalars(list source):
-    if not isinstance(source, list) or not isinstance(source[0], Scalar):
-        raise ValueError("source must be a list[Scalar]")
-
-
 # TODO: Could generalize list to sequence
 cpdef Table scalar_scatter(list source, Column scatter_map, Table target_table):
-    cdef unique_ptr[table] c_result
     cdef vector[reference_wrapper[const scalar]] source_scalars
-    cdef Scalar slr
-
-    _check_is_list_of_scalars(source)
-
-    for slr in source:
-        source_scalars.push_back(
-            reference_wrapper[constscalar](dereference(slr.c_obj))
-        )
+    source_scalars = _make_scalar_vector(source)
 
+    cdef unique_ptr[table] c_result
     with nogil:
         c_result = move(
             cpp_copying.scatter(
@@ -230,22 +233,13 @@ cpdef Table table_boolean_mask_scatter(Table input, Table target, Column boolean
 
 # TODO: Could generalize list to sequence
 cpdef Table scalar_boolean_mask_scatter(list input, Table target, Column boolean_mask):
-    _check_is_list_of_scalars(input)
-
-    cdef vector[reference_wrapper[const scalar]] c_scalars
-    c_scalars.reserve(len(input))
-
-    cdef Scalar slr
-    for slr in input:
-        c_scalars.push_back(
-            reference_wrapper[constscalar](dereference(slr.c_obj))
-        )
+    source_scalars = _make_scalar_vector(input)
 
     cdef unique_ptr[table] result
     with nogil:
         result = move(
             cpp_copying.boolean_mask_scatter(
-                c_scalars,
+                source_scalars,
                 target.view(),
                 boolean_mask.view(),
             )