Thanks, maybe I should get off my ass and contribute to the documentation
then ...

On 16 November 2016 at 22:30, Mark Dickinson <report@bugs.python.org> wrote:

>
> Mark Dickinson added the comment:
>
> > Is this behaviour documented? Or are you just expected to know what C
> does?
>
> Indeed, it's not as well documented as it should be. I think that's partly
> for historical reasons: before Python 2.7, Python's % formatting
> more-or-less delegated directly to the underlying C sprintf library
> function, and so just inherited whatever the behaviour of that function
> happened to be on the target operating system. Because the C standard
> doesn't make guarantees about the behaviour of %f for ties, Python wasn't
> in a position to do so either.
>
> But that excuse doesn't work any more with Python 2.7 and Python 3.x,
> where on most (but still not all) platforms, we're consistently rounding
> results using the usual round-ties-to-even rounding mode.
>
> There's a currently open issue (#17259) to improve the documentation here.
>
> ----------
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue28717>
> _______________________________________
>

-- 
Dr. William McIlhagga
Bradford School of Optometry & Vision Science,
Bradford University
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