[Python] Allow creating extension arrays via `pa.array` constructor

[rok]

Describe the enhancement requested

As noted in #44070 (comment) - it would be nice if we could shorten:

storage = pa.array(data, type=storage_type)
extension_type = pa.some_extension_type(storage_type)
array = pa.ExtensionArray.from_storage(extension_type, storage)

to:

extension_type = pa.some_extension_type(storage_type)
array = pa.array(data, extension_type)

Component(s)

Python

[khwilson]

I believe this already works. See https://github.com/apache/arrow/blob/main/python/pyarrow/array.pxi#L372 and this example:

from uuid import uuid4

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()

def main():
 data = [uuid4().bytes]
 arr = pa.array(data, type=UuidType())
 print(arr)

if __name__ == "__main__":
 main()

[rok]

Indeed it seem to have been covered by ARROW-17834. Thanks for noting this @khwilson !