Message 407990 - Python tracker (original) (raw)

I'll share a draft PR soon (excluding Decimal), so far it's still looking straightforward.

Maybe old versions would correctly ignore the new bit being set.

That's one of the benefits of using bit flags in an ABI: backward-compatible extensibility. (An implementation can defeat it by intentionally failing if unknown bits are encountered, but the code in question doesn't appear to be doing this.)

You can round explicitly before formatting

'%5.1f' % (round(-.00001, 1) + 0.0)

Yes, I have experience with it.

1. even as a one-off, it's questionable. If someone accidentally changes the precision in only one of the spec string or round call, that's a bug.
2. since applications and libraries may pass around format specs, and because of (1), you'll try to make a programmatic solution. Now you're parsing format spec strings.
3. while a programmatic solution can be done for a function API like format() that takes a separate spec and value, there is no sane way to wrap f-strings