Clarify which parameters are accepted by Traversable.open

Documentation

The docs for the open method of the importlib.resources.abc.Traversable protocol state:

When opening as text, accepts encoding parameters such as those accepted by io.TextIOWrapper.

It would be helpful to clarify exactly which parameters are accepted here. In particular, is the newline parameter covered by this? That parameter is accepted by io.TextIOWrapper, but is arguably not an "encoding parameter", so it's unclear whether it's supported.

An aside: typeshed does not seem to think that newline is supported here, but I'm wondering whether that might be a defect in typeshed. If the consensus here is that newline is supported, I'll open a typeshed issue.

The precise case I ran into was reading CSV data from a package resource. For portable CSV file reading, using newline="" is recommended, so I'm doing:

with csv_data.open(newline="") as f:
    reader = csv.DictReader(f)
    for row in reader:
        ... #  do something with row

where csv_data implements importlib.resources.abc.Traversable. The open call is flagged as invalid by mypy and pyright, but the code appears to work correctly (including in the case where the resource is zipfile-based).

If newline is not intended to be accepted here, then I guess I instead have to do:

with importlib.resources.as_file(csv_data) as csv_file:
    with csv_file.open(newline="") as f:
        reader = csv.DictReader(f)
        for row in reader:
            ... #  do something with row

That's fine, but it would be cleaner to be able to stream data straight from the resource without having to materialise the resource as a file first.

Linked PRs

• gh-137076
• gh-157294

リンク先の importlib.resources.abc ページにある Traversable.open のドキュメントから始め、次に open メソッドのドキュメント上および実際のパラメーター、特に encoding と newline を確認します。ドキュメントで newline を明示的に説明すべきか判断する前に、議論とリンクされている PR gh-137076 および gh-157294 を確認してください。受け入れられるパラメーターと想定される CSV の使用方法が明確になれば完了です。