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[Python-Dev] PEP 563: Postponed Evaluation of Annotations
Guido van Rossumguido at python.org
Fri Nov 3 10:40:48 EDT 2017
IMO the inability of referencing class-level definitions from annotationson methods pretty much kills this idea.On Thu, Nov 2, 2017 at 11:27 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:> On 3 November 2017 at 04:39, Jukka Lehtosalo <jlehtosalo at gmail.com> wrote:> >> > * forward references: when a type hint contains names that have not> been> >> > defined yet, that definition needs to be expressed as a string> >> > literal;> >>> >> After all the discussion, I still don't see why this is an issue.> >> Strings makes perfectly fine forward references. What is the problem> >> that needs solving? Is this about people not wanting to type the leading> >> and trailing ' around forward references?> >> >> > Let's make a thought experiment. What if every forward reference would> > require special quoting? Would Python programmers be happy with this?> Say,> > let's use ! as a suffix to mark a forward reference. They make perfectly> > fine forward references. They are visually pretty unobtrusive (I'm not> > suggesting $ or other ugly perlisms):> >> > def main():> > args = parse_args!() # A forward reference> > do_stuff!(args) # Explicit is better than implicit> >> > def parse_args():> > ...> >> > def do_stuff(args):> > ...> >> > Of course, I'm not seriously proposing this, but this highlights the fact> > that in normal code forward references "just work" (at least usually),> and> > if we'd require a special quoting mechanism to use them anywhere, Python> > would look uglier and more inconsistent. Nobody would be happy with this> > change, even though you'd only have to type a single ! character extra --> > that's not a lot work, right?> >> > I think that the analogy is reasonable.>> I think it also makes a pretty decent argument that pushing function> annotations into implicit lambda expressions will be easier to explain> to people than converting them into strings, and then having to> explain an entirely new complex set of name resolution rules.>> Cheers,> Nick.>> --> Nick Coghlan |ncoghlan at gmail.com | Brisbane, Australia> _______________________________________________> Python-Dev mailing list>Python-Dev at python.org>https://mail.python.org/mailman/listinfo/python-dev> Unsubscribe:https://mail.python.org/mailman/options/python-dev/> guido%40python.org>-- --Guido van Rossum (python.org/~guido)-------------- next part --------------An HTML attachment was scrubbed...URL: <http://mail.python.org/pipermail/python-dev/attachments/20171103/101278de/attachment.html>
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