wjones127 commented on code in PR #13454:
URL: https://github.com/apache/arrow/pull/13454#discussion_r908769271
##########
docs/source/python/extending_types.rst:
##########
@@ -286,6 +286,36 @@ are available).
The same ``__arrow_ext_class__`` specialization can be used with custom types
defined
by subclassing :class:`ExtensionType`.
+Custom scalar conversion
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+If you want scalars of your custom extension type to convert to a custom type
when
+:meth:`ExtensionScalar.as_py()` is called, you can override the
:meth:`ExtensionType.scalar_as_py()`
+method. For example, if we wanted the above example 3D point type to return a
tuple instead
+of a list, we would implement::
+
+ Point3D = namedtuple("Point3D", ["x", "y", "z"])
+
+ class Point3DType(pa.PyExtensionType):
+ def __init__(self):
+ pa.PyExtensionType.__init__(self, pa.list_(pa.float32(), 3))
+
+ def __reduce__(self):
+ return Point3DType, ()
+
+ def scalar_as_py(self, scalar):
+ if scalar is None:
+ return None
+ else:
+ return Point3D(*scalar.as_py())
+
+Arrays built using this extension scalar type now have the expected scalar
behaviour::
Review Comment:
```suggestion
Arrays built using this extension type now provide scalars that convert to
our ``Point3D`` class::
```
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