[Python-ideas] PEP 505: None-aware operators

[Steve Dower]

Just for fun, I decided to go through some recently written code by some genuine Python experts (without their permission...) to see what changes would be worth taking. So I went to the sources of our github bots.

Honestly, I only found three places that were worth changing (though I'm now kind of leaning towards ?[] eating LookupError, since that seems much more useful when traversing the result of json.loads()...). I'm also not holding up the third one as the strongest example :)


>From https://github.com/python/miss-islington/blob/master/miss_islington/status_change.py:

async def check_status(event, gh, *args, **kwargs):
    if (
        event.data["commit"].get("committer")
        and event.data["commit"]["committer"]["login"] == "miss-islington"
    ):
        sha = event.data["sha"]
        await check_ci_status_and_approval(gh, sha, leave_comment=True)

After:

async def check_status(event, gh, *args, **kwargs):
    if event.data["commit"].get("committer")?["login"] == "miss-islington":
        sha = event.data["sha"]
        await check_ci_status_and_approval(gh, sha, leave_comment=True)


>From https://github.com/python/bedevere/blob/master/bedevere/__main__.py:

        try:
            print('GH requests remaining:', gh.rate_limit.remaining)
        except AttributeError:
            pass

Assuming you want to continue hiding the message when no value is available:
        if (remaining := gh.rate_limit?.remaining) is not None:
            print('GH requests remaining:', remaining)

Assuming you want the message printed anyway:
        print(f'GH requests remaining: {gh.rate_limit?.remaining ?? "N/A"}')


>From https://github.com/python/bedevere/blob/master/bedevere/news.py (this is the one I'm including for completeness, not because it's the most compelling example I've ever seen):

async def check_news(gh, pull_request, filenames=None):
    if not filenames:
        filenames = await util.filenames_for_PR(gh, pull_request)

After:
async def check_news(gh, pull_request, filenames=None):
    filenames ??= await util.filenames_for_PR(gh, pull_request)


On 19Jul2018 2222, Steven D'Aprano wrote:
> In other words, we ought to be comparing the expressiveness of
> 
>      process(spam ?? something)
> 
> versus:
> 
>     process(something if spam is None else spam)

Agreed, though to make it a more favourable comparison I'd replace "spam" with "spam()?.eggs" and put it in a class/module definition where you don't want temporary names leaking ;)

Cheers,
Steve