[ARROW-15839] [C++][Python] Allow to reconstruct a ListArray with ListArray.from_arrays and keep the nulls

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 7.0.0
• Fix Version/s: 10.0.0
• Component/s: C++, Python
• Labels: good-second-issue pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/31279
• Assignee: Miles Granger
• Reporter: quentin lhoest
• Created: 03/Mar/22 18:01
• Updated: 11/Jan/23 11:40
• Resolved: 01/Sep/22 10:34

Description

Hi ! Right now when one wants to reconstruct a ListArray using ListArrar.from_arrays, the `null` values may be lost:

import pyarrow as pa

arr = pa.array([None, [0]])
reconstructed_arr = pa.ListArray.from_arrays(arr.offsets, arr.values)
print(reconstructed_arr.to_pylist())
# [[], [0]] 

It would be nice to have a `mask` parameter to `ListArray.from_arrays` (or any way to provide the validity bitmap) to be able to reconstruct the original array with the `null` values.

It would also be consistent with `StructArray.from_arrays` that already has the `mask` parameter.

Issue Links

• links to: GitHub Pull Request #13894