[Python-ideas] Binary f-strings

[Sven R. Kunze]

On 28.09.2015 03:23, Eric V. Smith wrote:
> The only real question is: what encoding to use for the second parameter
> to bytes()? Since an object must return unicode from __format__(), I
> need to convert that to bytes in order to join everything together. But how?

Cf. https://www.python.org/dev/peps/pep-0461/#interpolation


It says:

b"%x" % val

is equivalent to:

("%x" % val).encode("ascii")


So, ASCII would make a lot of sense to me as well.


> Here I suggest 'ascii'. Unfortunately, this would give an error if
> __format__ returned anything with a char greater than 127. I think we've
> learned that an API that only raises an exception with certain specific
> inputs is fragile.

Could you be more specific here?


Best,
Sven