[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 !