On 1/21/2014 10:59 AM, Yury Selivanov wrote:
There is one more, hopefully last, open urgent question with the signature
object. At the time we were working on the PEP 362, PEP 457 didn’t
exist. Nor did we have any function with real positonal-only parameters,
since there was no Argument Clinic yet. However, I implemented
rudimentary support for them:
“Parameter.POSITIONAL_ONLY” constant;
“Signature.bind” and “Signature.bind_partial” fully support functions
with positional-only parameters;
“Signature.__str__” renders them distinctively from other kinds.
The last point is the troublesome now. "Signature.__str__” renders
positional-only parameters in ‘<>’ brackets, so in:
foo(<ham>, <spam>, baz)
This amounts to a hidden new API.
“ham” and “spam” are positional-only. The choice of angle brackets was
unfortunate, as, first of all, this wasn’t really discussed on
python-dev, and second, it’s easy to think that those parameters are
optional.
Now, with the AC landing in 3.4, we need to decide how positional-only
parameters will look like.
Without starting a new discussion similar to what we had prior to PEP 457,
I think we have three options:
1. Leave it as is. Obviously, the downside is the potential confusion
with “optional” notation.
I think this this is bad, as it has not been discussed and agreed on,
and might be changed. It is a plausible alternative to '/', but might
possibly even have been rejected. I do not remember.
2. Adopt PEP 457 style: using “/“ to separate positional-only parameters
from the rest.
I think this is what Larry proposed, but Nick opposed as a post-beta new
feature.
3. Don’t use any notation, just render them as plain arguments:
"foo(ham, spam, baz)". The downside here is that the users will be
confused, and might try passing those parameters with keywords, or
binding them with keywords.
This is the status quo for the docs (both notation and occasional
confusion). I think signature should match until we agree on a new
convention (and I think one is needed). The first thing to decide is
whether to mark each position-only parameter or to put one marker after
all of them.
--
Terry Jan Reedy
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
