ianmcook commented on code in PR #43849:
URL: https://github.com/apache/arrow/pull/43849#discussion_r1733604630
##########
python/pyarrow/types.pxi:
##########
@@ -2089,30 +2120,41 @@ def unregister_extension_type(type_name):
Examples
--------
- Define a UuidType extension type subclassing ExtensionType:
+ Define a RationalType extension type subclassing ExtensionType:
>>> import pyarrow as pa
- >>> class UuidType(pa.ExtensionType):
- ... def __init__(self):
- ... pa.ExtensionType.__init__(self, pa.binary(16), "my_package.uuid")
- ... def __arrow_ext_serialize__(self):
- ... # since we don't have a parameterized type, we don't need extra
- ... # metadata to be deserialized
- ... return b''
- ... @classmethod
- ... def __arrow_ext_deserialize__(self, storage_type, serialized):
- ... # return an instance of this subclass given the serialized
- ... # metadata.
- ... return UuidType()
- ...
+ >>> import pyarrow.types as pt
+ >>> class RationalType(pa.ExtensionType):
+ ... def __init__(self, data_type: pa.DataType):
+ ... if not pt.is_integer(data_type):
+ ... raise TypeError(f"data_type must be an integer type not
{data_type}")
+ ... super().__init__(
+ ... pa.struct(
+ ... [
+ ... ("numer", data_type),
+ ... ("denom", data_type),
+ ... ],
+ ... ),
+ ... # N.B. This name does _not_ reference `data_type` so
deserialization
+ ... # will work for _any_ integer `data_type` after
registration
+ ... "my_package.rational",
+ ... )
+ ... def __arrow_ext_serialize__(self) -> bytes:
+ ... # No serialized metadata necessary
+ ... return b""
+ ... @classmethod
+ ... def __arrow_ext_deserialize__(self, storage_type, serialized):
Review Comment:
```suggestion
... def __arrow_ext_deserialize__(cls, storage_type, serialized):
```
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