On Sat, Sep 26, 2020 at 10:43:01PM +0100, Nicholas Cole wrote:
> I don't find such examples a conclusive argument in favour of this
> syntax at all.
I wouldn't expect you would -- Stefano made it up as an example of
something that he felt was a poor use of subscripts!
You should not be
On Sat, Sep 26, 2020 at 11:49 PM Guido van Rossum wrote:
> On Sat, Sep 26, 2020 at 7:44 PM Ricky Teachey wrote:
>
>> The problem is that there is lots of existing code like this:
>>
>> def __setitem__(self, index, value): ...
>>
>> But the new features will almost certainly lead people to write
On Sat, Sep 26, 2020 at 7:44 PM Ricky Teachey wrote:
> The problem is that there is lots of existing code like this:
>
> def __setitem__(self, index, value): ...
>
> But the new features will almost certainly lead people to write new code
> like this:
>
> d={}
> obj[**d] = "foo" # no kwd
On Sat, Sep 26, 2020 at 01:47:56PM -0300, Sebastian Kreft wrote:
> In this fashion have you considering having keyword only indices, that is
> to only allow either obj[1, 2] or obj[row=1, col=2] (if the class supports
> it), and disallow mixing positional and keyword indices, meaning obj[1,
>
On Sat, Sep 26, 2020, 11:30 PM Greg Ewing
wrote:
> On 27/09/20 3:43 pm, Ricky Teachey wrote:
> > telling people "either provide a default argument for
> > both index AND value in your __setitem__ method, or neither" is also a
> > perfectly legitimate way forward.
>
> Giving the value parameter
On 27/09/20 3:43 pm, Ricky Teachey wrote:
telling people "either provide a default argument for
both index AND value in your __setitem__ method, or neither" is also a
perfectly legitimate way forward.
Giving the value parameter of a __setitem__ a default seems like a
weird thing to do, since
On Sat, Sep 26, 2020 at 10:43 PM Ricky Teachey wrote:
> ...which, if someone does this arbitrarily against classes that use the
> existing kind of code I gave at the first, will call (if the sentinel is ()
> ):
>
> obj.__setitem__(())
>
> ...which could have all kinds of weird effects rather
On Sat, Sep 26, 2020 at 10:30 PM Ben Rudiak-Gould
wrote:
> I don't understand the problem here.
>
> d[p=q] --> d.__{get,set,del}item__((), ..., p=q)
> d[1, p=q] --> d.__{get,set,del}item__((1), ..., p=q)
> d[1, 2, p=q] --> d.__{get,set,del}item__((1, 2), ..., p=q)
> d[1, 2,
On Sat, Sep 26, 2020 at 09:59:27AM +0200, Sascha Schlemmer via Python-ideas
wrote:
> I think a clear distinction has to be made between errors that belong
> to the api surface of a function e.g. some `ValueError` or
> `ZeroDivisionError` and *exceptional* errors e,g.`KeyboardInterrupt`
> or
I don't understand the problem here.
d[p=q] --> d.__{get,set,del}item__((), ..., p=q)
d[1, p=q] --> d.__{get,set,del}item__((1), ..., p=q)
d[1, 2, p=q] --> d.__{get,set,del}item__((1, 2), ..., p=q)
d[1, 2, 3, p=q] --> d.__{get,set,del}item__((1, 2, 3), ..., p=q)
d[1,
On Sun, Sep 27, 2020 at 8:49 AM Christopher Barker wrote:
>
>
> On Fri, Sep 25, 2020 at 11:50 PM Steven D'Aprano wrote:
> >>
> >> 1. We have to pass a sentinel to the setitem dunder if there is no
> >> positional index passed.
>
>
> I still don't follow this logic -- why can't nothing be passed?
Another inconsistency is that the case of keyword arguments only would bind
the RHS value to the first positional argument, which is the index, and not
the value. I think this is what Guido was referring to when he responded
talking about introspection being required? Not sure.
in any case, to me
On Fri, Sep 25, 2020 at 11:50 PM Steven D'Aprano
wrote:
>>
>> 1. We have to pass a sentinel to the setitem dunder if there is no
>> positional index passed.
I still don't follow this logic -- why can't nothing be passed? The dunders
either require an index or they don't, would that be just like
On Sat, Sep 26, 2020 at 11:45 AM Nicholas Cole
wrote:
> > I think this is a very natural looking use case, and is not as well
> addressed by putting the multiplier outside the indexing. Imagine you have
> two arrays that store lengths, but not necessarily in the same units.
> Whatever the
On Sat, Sep 26, 2020 at 2:44 PM Nicholas Cole
wrote:
> I can't help feeling that this is a syntax looking for a set of
> solutions to apply itself to. It will add enormous complexity
> (together, no doubt, with speed issues and backwards-compatibility
> issues) to the language, and I'm not sure
On Sat, Sep 26, 2020 at 9:35 PM David Mertz wrote:
>
> On Sat, Sep 26, 2020 at 12:50 AM Stefano Borini
> wrote:
>>
>> Other use cases are certainly allowed, but to me, something like
>>
>> a[1, 2, unit="meters"]
>> a[1, 2, unit="meters"] = 3
>>
>> makes me feel uncomfortable, although I might
On Sat, Sep 26, 2020 at 10:47 PM Sascha Schlemmer via Python-ideas
wrote:
> ```
> def div(a: int, b: int) -> Result[float, ZeroDivisionError]:
> try:
> return Success(a / b)
> except ZeroDivisionError as error:
> return Failure(error)
> ```
>
> Now `div` does return a valid
On Sat, Sep 26, 2020 at 12:50 AM Stefano Borini
wrote:
> Other use cases are certainly allowed, but to me, something like
>
> a[1, 2, unit="meters"]
> a[1, 2, unit="meters"] = 3
makes me feel uncomfortable, although I might learn to accept it.
Then why isn't the unit close to 3, as in
>
>
On 9/25/2020 1:34 PM, Paul Bryan wrote:
On Fri, 2020-09-25 at 18:19 +0200, Marco Sulla wrote:
That I hope it's not the place where this proposal will be sent.
My idea is apparently simple: what if, anytime we create an object,
instead of deleting it, we send it in a trash bin? If the object
On Fri, Sep 25, 2020 at 11:26 PM Ricky Teachey wrote:
> On Sat, Sep 26, 2020 at 1:51 AM Guido van Rossum wrote:
>
>> But this requires introspection.
>>
>
> I'm sorry Guido I'm staring at your message and reread mine several times
> and I don't understand where introspection is required. It
On Sat, Sep 26, 2020 at 7:51 AM Stefano Borini
wrote:
> On Sat, 26 Sep 2020 at 04:02, Steven D'Aprano wrote:
>
> > Did you just completely undermine the rationale for your own PEP?
> >
> > Isn't the entire purpose of this PEP to allow subscripts to include
> > keyword arguments? And now you are
On Sat, Sep 26, 2020 at 8:50 AM Sascha Schlemmer via Python-ideas <
python-ideas@python.org> wrote:
> I think a clear distinction has to be made between errors that belong to
> the api surface of a function e.g. some `ValueError` or `ZeroDivisionError`
> and *exceptional* errors
On Fri, Sep 25, 2020 at 3:38 PM Steven D'Aprano wrote:
> The last thing I want to see is people being encouraged to write code
> like this:
>
> def demo(arg)->Something:
[... elided ...]
> except:
> # Any other unexpected error.
> raise
I think a clear distinction has to be made between errors that belong to the
api surface of a function e.g. some `ValueError` or `ZeroDivisionError` and
*exceptional* errors e,g.`KeyboardInterrupt` or `DatabaseExplodedError`. For
the latter case exceptions work perfectly well as they are and it
On Sat, 26 Sep 2020 at 04:02, Steven D'Aprano wrote:
> Did you just completely undermine the rationale for your own PEP?
>
> Isn't the entire purpose of this PEP to allow subscripts to include
> keyword arguments? And now you are describing it as "poor design"?
Not really. to _me_, an indexing
On Sat, 26 Sep 2020 at 05:10, Steven D'Aprano wrote:
>
> I recommend that the PEP be changed to allow `*args` inside subscripts.
Will do.
--
Kind regards,
Stefano Borini
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On Fri, Sep 25, 2020 at 08:52:45PM -1000, David Mertz wrote:
> On Fri, Sep 25, 2020, 5:49 PM Steven D'Aprano
>
> > Since both None and () are likely to be legitimate indexes, and
> > NotImplemented is less likely to be such, I think this supports using
> > NotImplemented.
> >
>
> I think your
On Sat, Sep 26, 2020 at 01:43:18AM -0400, Ricky Teachey wrote:
> On Fri, Sep 25, 2020 at 11:50 PM Steven D'Aprano
> wrote:
>
> > TL;DR:
> >
> > 1. We have to pass a sentinel to the setitem dunder if there is no
> > positional index passed. What should that sentinel be?
> >
>
> Isn't there a
On Fri, Sep 25, 2020, 5:49 PM Steven D'Aprano
> Since both None and () are likely to be legitimate indexes, and
> NotImplemented is less likely to be such, I think this supports using
> NotImplemented.
>
I think your arguments for NotImplemented vs None or () are solid. But I'm
having trouble
On Sat, Sep 26, 2020 at 1:51 AM Guido van Rossum wrote:
> But this requires introspection.
>
I'm sorry Guido I'm staring at your message and reread mine several times
and I don't understand where introspection is required. It seems like all
the parser has to do is what it has always done-- pass
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