I could absolutely see a lot of use for this when it comes to rebinding names in callbacks and the like.
for i in range(10): callLater(delay, lambda i=: print(i)) But with this being a very common scenario for such a feature being needed, we'd see a lot of confusion with how much that looks like a walrus operator. I am +1 on the feature, but -1 on the syntax. On Thu, Apr 16, 2020 at 12:45 PM Steven D'Aprano <st...@pearwood.info> wrote: > Do any other languages already have this feature? > > Can you show some actual real-life code that would benefit from this, as > opposed to pretend code like: > > foo(bar=, qux=) > > I think that if I had seen this syntax as a beginner, I would have had > absolutely no idea how to interpret it. I probably would have decided > that Python was an unreadably cryptic language and gone on to learn > something else. > > Of course, with 20+ years of experience reading and writing code, I > know better now. I would interpret it as setting bar and qux to some > kind of Undefined value. > > I am very sympathetic to the rationale: > > "it is quite common to find code that forwards keyword parameters having > to re-state keyword arguments names" > > and I've discussed similar/related issues myself, e.g. here: > > https://mail.python.org/pipermail/python-list/2018-February/881615.html > > But I am not convinced that adding magic syntax to implicitly guess the > value wanted as argument if it happens to match the parameter name is a > good design feature. > > Is being explicit about the value that you are passing to a parameter > really such a burden that we need special syntax to avoid stating what > value we are using as the argument? > > I don't think it is. And I would far prefer to read explicit code like > this: > > # Slightly modified from actual code. > self.do_something( > meta=meta, > dunder=dunder, > private=private, > invert=invert, > ignorecase=ignorecase, > ) > > over the implicit version: > > # Looks like code I haven't finished writing :-( > self.do_something(meta=, dunder=, private=, invert=, ignorecase=) > > > Out of the millions of possible values we might pass, I don't think that > the func(spam=spam) case is so special that we want to give it special > syntax. > > -- > Steven > _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/VCCQ6BOVEQZ4ZWLKVDTVUCMAWD2VQL7B/ > Code of Conduct: http://python.org/psf/codeofconduct/ > > -- CALVIN SPEALMAN SENIOR QUALITY ENGINEER cspea...@redhat.com M: +1.336.210.5107 [image: https://red.ht/sig] <https://red.ht/sig> TRIED. TESTED. TRUSTED. <https://redhat.com/trusted>
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