GH-49384: [Python] Respect copy=True in ChunkedArray.__array__

[jingyi-zhao-01]

Rationale for this change

ChunkedArray.__array__(copy=True) should respect NumPy's copy request. For a single-chunk ChunkedArray, the current path can return a zero-copy read-only NumPy view instead.

Closes #49384.

What changes are included in this PR?

• Make ChunkedArray.__array__(copy=True) return a real NumPy copy.
• Add a regression test for the single-chunk case.

Are these changes tested?

Yes:

python -m pytest python/pyarrow/tests/test_table.py -q

Are there any user-facing changes?

Yes. np.array(pa.chunked_array([[...]]), copy=True) now returns a writable copied NumPy array, matching the behavior users expect from copy=True.

AI assistance

I used an codex while preparing this patch. I reviewed the change myself, kept it scoped to ChunkedArray.__array__, and verified it with the focused PyArrow table tests above.

• GitHub Issue: [Python] Single chunk ChunkedArray doesn't correctly respect copy in __array__method #49384

[github-actions]

Thanks for opening a pull request!

If this is not a minor PR. Could you open an issue for this pull request on GitHub? https://github.com/apache/arrow/issues/new/choose

Opening GitHub issues ahead of time contributes to the Openness of the Apache Arrow project.

Then could you also rename the pull request title in the following format?

GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

MINOR: [${COMPONENT}] ${SUMMARY}

See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[github-actions]

⚠️ GitHub issue #49384 has been automatically assigned in GitHub to PR creator.