[ARROW-8572] [Python] Expose UnionArray.array and other fields

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.17.0
• Fix Version/s: 1.0.0
• Component/s: Python
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/24738
• Assignee: David Li
• Reporter: David Li
• Created: 23/Apr/20 19:19
• Updated: 11/Jan/23 08:01
• Resolved: 28/Apr/20 20:08

Description

Currently in Python, you can construct a UnionArray easily, but getting the data back out (without copying) is near-impossible. We should expose the getter for UnionArray.array so we can pull out the constituent arrays. We should also expose fields like mode while we're at it.

The use case is: in Flight, we'd like to write multiple distinct datasets (with distinct schemas) in a single logical call; using UnionArrays lets us combine these datasets into a single logical dataset.

Issue Links

• duplicates: ARROW-5869 [Python] Need a way to access UnionArray's children as Arrays in pyarrow
• links to: GitHub Pull Request #7027