[Python] Support ExtentionType on conversion to numpy/pandas

[asfimport]

Currently converting a Table of RecordBatch with an ExtensionType array to pandas gives:

ArrowNotImplementedError: No known equivalent Pandas block for Arrow data of type extension<arrow.py_extension_type> is known.

And similarly converting the array itself to a python object (to_pandas or to_pylist) gives an ArrowNotImplementedError or a "KeyError: 28"

Initial support could be to fall back to the storage type.

Reporter: Joris Van den Bossche / @jorisvandenbossche
Assignee: Joris Van den Bossche / @jorisvandenbossche

PRs and other links:

• GitHub Pull Request #5826

_{Note: This issue was originally created as ARROW-5859. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 5826
#5826