[ARROW-8131] [Python] Add dynamic attributes to PyArrow ExtensionArray

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Won't Do
• Affects Version/s: 0.16.0
• Component/s: Python
• Labels: Python3 pull-request-available
• Environment: Ubuntu 19.10 + Python 3.7
• External issue URL: https://github.com/apache/arrow/issues/24338
• Assignee: Unassigned
• Reporter: Paul Balanca
• Created: 16/Mar/20 09:59
• Updated: 11/Jan/23 07:58
• Resolved: 24/Mar/20 19:05

Description

In the present implementation, the interface of the class `ExtensionArray` is not extendable by user. One can not easily inherit from it, as the constructor _init_ can not be called directly, or it does not allow adding dynamically atttributes.

Keeping the current design with build methods `from_*`, I believe it could then make sense to allow dynamic attributes in `ExtensionArray` (see https://cython.readthedocs.io/en/latest/src/userguide/extension_types.html#dynamic-attributes). The runtime & size cost of the Python objects would be fairly minimal, compared to increased flexibility it would allow.

A typical use case where it could be useful would be dynamic mixins (added by custom Factory), allowing projects based on PyArrow to extend (! ) the interface with specific business logic. 

Issue Links

• is related to: ARROW-6176 [Python] Allow to subclass ExtensionArray to attach to custom extension type
• links to: GitHub Pull Request #6630