[jira] [Commented] (ARROW-840) [Python] Provide Python API for creating user-defined data types that can survive Arrow IPC

["Robert Nishihara (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-840?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15970558#comment-15970558 ] 

Robert Nishihara commented on ARROW-840:
----------------------------------------

Is "user-defined" data types intended to include arbitrary custom Python classes?

{code}
class Foo(object):
  def __init__(self):
    ...
{code}

For example, if we wish to pass a {{Foo}} object through Arrow IPC, what would the custom metadata be? Would it be the pickled class definition? Would it be something like the string {{"Foo"}}?

> [Python] Provide Python API for creating user-defined data types that can survive Arrow IPC
> -------------------------------------------------------------------------------------------
>
>                 Key: ARROW-840
>                 URL: https://issues.apache.org/jira/browse/ARROW-840
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: Python
>            Reporter: Wes McKinney
>
> The user will provide:
> * Data type subclass that can indicate the physical storage type
> * "get state" and "set state" functions for serializing custom metadata to bytes
> * An optional function for "boxing" scalar values from the physical array storage
> Internally, this will build on an analogous C++ API for defining user data types



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