[jira] [Created] (ARROW-5271) [Python] Interface for converting pandas ExtensionArray / other custom array objects to pyarrow Array

["Joris Van den Bossche (JIRA)" <ji...@apache.org>]

Joris Van den Bossche created ARROW-5271:
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             Summary: [Python] Interface for converting pandas ExtensionArray / other custom array objects to pyarrow Array
                 Key: ARROW-5271
                 URL: https://issues.apache.org/jira/browse/ARROW-5271
             Project: Apache Arrow
          Issue Type: Improvement
          Components: Python
            Reporter: Joris Van den Bossche


Related to ARROW-2428, which describes the issue to convert back to an ExtensionArray in {{to_pandas}}.

To start supporting to convert custom ExtensionArrays (eg the nullable Int64Dtype in pandas, or the arrow-backed fletcher arrays, ...) to arrow Arrays (eg in {{pyarrow.array(..)}}), I think it would be good to define an interface or hook that external projects can implement and that pyarrow will call if available. 
This would allow external projects to define how they can be converted to arrow arrays, without the need that pyarrow itself starts to gather a lot of special cased code for certain types (like pandas' nullable Int64).

This could similar to how numpy looks for the {{__array__}} method, so we might call it {{__arrow_array__}}.

See also https://github.com/pandas-dev/pandas/issues/20612 for an issue discussing this on the pandas side.



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