[GitHub] [arrow] sjperkins commented on a diff in pull request #34469: GH-33801: [Python] Further expose C++ Extension Types in Python

["sjperkins (via GitHub)" <gi...@apache.org>]

sjperkins commented on code in PR #34469:
URL: https://github.com/apache/arrow/pull/34469#discussion_r1126521520


##########
python/pyarrow/tests/test_extension_type.py:
##########
@@ -1115,9 +1115,16 @@ def test_cpp_extension_in_python(tmpdir):
     assert uuid_type.extension_name == "uuid"
     assert uuid_type.storage_type == pa.binary(16)
 
+    array_cls = uuid_type.__arrow_ext_class__()
+    scalar_cls = uuid_type.__arrow_ext_scalar_class__()
+    assert array_cls.__name__ == "ExtensionArray(uuid)"
+    assert scalar_cls.__name__ == "ExtensionScalar(uuid)"

Review Comment:
   The auto-generated class naming schema is similar to that of BaseExtensionType. i.e. `BaseExtensionType(extension<uuid>)`.



##########
python/pyarrow/tests/test_extension_type.py:
##########
@@ -1115,9 +1115,16 @@ def test_cpp_extension_in_python(tmpdir):
     assert uuid_type.extension_name == "uuid"
     assert uuid_type.storage_type == pa.binary(16)
 
+    array_cls = uuid_type.__arrow_ext_class__()
+    scalar_cls = uuid_type.__arrow_ext_scalar_class__()
+    assert array_cls.__name__ == "ExtensionArray(uuid)"
+    assert scalar_cls.__name__ == "ExtensionScalar(uuid)"
+
     array = mod._make_uuid_array()
     assert array.type == uuid_type
+    assert isinstance(array, array_cls)

Review Comment:
   prior to this change, only `isinstance(array, pyarrow.ExtensionArray)` would have held.



##########
python/pyarrow/tests/test_extension_type.py:
##########
@@ -1127,3 +1134,12 @@ def test_cpp_extension_in_python(tmpdir):
     reconstructed_array = batch.column(0)
     assert reconstructed_array.type == uuid_type
     assert reconstructed_array == array
+
+    storage = pa.array([b'0onmlkjihgfedcba']*4, pa.binary(16))
+    ext_array = pa.ExtensionArray.from_storage(uuid_type, storage)
+    assert isinstance(ext_array, array_cls)

Review Comment:
   From memory, before to this change, `pa.ExtensionArray.from_storage` would have returned a `pyarrow.ExtensionArray`.



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