ENH (string dtype): accept string_view in addition to string/large_string for ArrowStringArray input (#60222)

Author: jorisvandenbossche

pandas/core/arrays/string_arrow.py

@@ -17,6 +17,7 @@
 from pandas.compat import (
     pa_version_under10p1,
     pa_version_under13p0,
+    pa_version_under16p0,
 )
 from pandas.util._exceptions import find_stack_level
 
@@ -71,6 +72,10 @@ def _chk_pyarrow_available() -> None:
         raise ImportError(msg)
 
 
+def _is_string_view(typ):
+    return not pa_version_under16p0 and pa.types.is_string_view(typ)
+
+
 # TODO: Inherit directly from BaseStringArrayMethods. Currently we inherit from
 # ObjectStringArrayMixin because we want to have the object-dtype based methods as
 # fallback for the ones that pyarrow doesn't yet support
@@ -128,11 +133,13 @@ def __init__(self, values) -> None:
         _chk_pyarrow_available()
         if isinstance(values, (pa.Array, pa.ChunkedArray)) and (
             pa.types.is_string(values.type)
+            or _is_string_view(values.type)
             or (
                 pa.types.is_dictionary(values.type)
                 and (
                     pa.types.is_string(values.type.value_type)
                     or pa.types.is_large_string(values.type.value_type)
+                    or _is_string_view(values.type.value_type)
                 )
             )
         ):

pandas/tests/arrays/string_/test_string_arrow.py

@@ -99,6 +99,20 @@ def test_constructor_valid_string_type_value_dictionary(string_type, chunked):
     assert pa.types.is_large_string(arr._pa_array.type)
 
 
+@pytest.mark.parametrize("chunked", [True, False])
+def test_constructor_valid_string_view(chunked):
+    # requires pyarrow>=18 for casting string_view to string
+    pa = pytest.importorskip("pyarrow", minversion="18")
+
+    arr = pa.array(["1", "2", "3"], pa.string_view())
+    if chunked:
+        arr = pa.chunked_array(arr)
+
+    arr = ArrowStringArray(arr)
+    # dictionary type get converted to dense large string array
+    assert pa.types.is_large_string(arr._pa_array.type)
+
+
 def test_constructor_from_list():
     # GH#27673
     pytest.importorskip("pyarrow")