GH-38857: [Python] Add append mode for pyarrow.OsFile

[milesgranger]

Rationale for this change

Seems reasonable. :)

What changes are included in this PR?

Exposes the C++ append parameter from FileOutputStream to PyArrow's OSFile.

Are these changes tested?

Yes.

Are there any user-facing changes?

Can add a or ab to mode parameter in pyarrow.OsFile

• Closes: [Python] Expose append parameter from FileOutputStream::Open #38857

[raulcd]

Thanks for the PR @milesgranger !
This PR doesn't seem to fit our definition for MINOR, as it should be only about minor documentation changes.
Could you please create a GitHub issue and update the PR title accordingly?
Thanks!

[github-actions]

⚠️ GitHub issue #38857 has been automatically assigned in GitHub to PR creator.

[milesgranger]

Ah, how embarrassing. Issue created and and title updated as requested!

[AlenkaF]

Hi @milesgranger, thank you for the PR!
LGTM +1

Would only add an example to the docstrings of the OSFile class. It would maybe also be worth adding a test to test_native_file_modes?

[milesgranger]

Thanks for the review @AlenkaF.
In adding the doc example and looking at test_native_file_modes, I see that NativeFile.mode plays only with 'is_readable' and 'is_writable'.

Should I go about adding a is_appendable to facilitate returning an 'ab'?

---

Edit: happy to do a follow up as well. Whichever is easier for you all.

[AlenkaF]

Ah, thank you for looking into it.

I am not sure how to handle 'ab' mode in connection to the NativeFile class. I do not see an issue if OSFile subclass handles extra append mode and NativeFile does not. @jorisvandenbossche what do you think?

[pitrou]

Should I go about adding a is_appendable to facilitate returning an 'ab'?

You could add a private _is_appending attribute that would default to False.

[milesgranger]

Failure seems unrelated.

[AlenkaF]

I have rerun it just in case.
LGTM otherwise, thank you!

[raulcd]

I also think is unrelated. I've opened #39003 to track it.

[AlenkaF]

Thanks! 👋

[jorisvandenbossche]

Thanks Miles! ;)

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 6 benchmarking runs that have been run so far on merge-commit 92fe831.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 5 possible false positives for unstable benchmarks that are known to sometimes produce them.