+1 on the idea.
Sometimes early binding is needed, sometimes late binding is needed. So
Python should provide both. QED 😁
I'm not keen on the
var = > expr
syntax. IMO the arrow is pointing the wrong way. expr is assigned to var.
Some possible alternatives, if there is no technical reaso
On 10/23/21 8:04 PM, Bruce Leban wrote:
> I was talking about (2) but I should have been explicit. And yes, you
highlight a potential source of confusion.
>
> def f(x=>x + 1): ...
>
> means that x is 1 more than the value of x from the enclosing global scope
(at function call time) while
Uh, n
On Sun, Oct 24, 2021 at 05:24:46PM +0400, Abdulla Al Kathiri wrote:
> It’s not a good idea to use a mutable object anyways a default value.
Unless you intend to use a mutable object as a default value, and have
it persist from one call to the next. Then it is absolutely fine.
One of the use-cas
+1 to this idea -- thanks Chris A!
On Sat, Oct 23, 2021 at 2:01 PM Bruce Leban wrote:
> Here's one way you could imagine writing this today:
>>
>
> def bisect(a, x, lo=0, hi=lambda: len(a)):
> hi = hi() if callable(hi) else hi
> ...
>
> which is clumsy and more importantly do
On 24/10/2021 03:48, Steven D'Aprano wrote:
On Sun, Oct 24, 2021 at 01:16:02PM +1100, Chris Angelico wrote:
And is it really a problem if we delay the late-binding to the point
where the value is actually needed? Here's a toy example:
# Using only early binding.
def function(spam,
More about thunks. I've resisted the temptation to look at the Wikipedia
page -- this is from memory.
On Sat, Oct 23, 2021 at 11:39 PM Steven D'Aprano
wrote:
> > I would prefer to see this situation handled as part of a
> > larger-scale
> > change of adding some kind of "inline lambd
Yeah I realized that when I went to my laptop hhh. Hence the previous email
correcting it.
> On 24 Oct 2021, at 5:19 PM, Steven D'Aprano wrote:
>
> On Sun, Oct 24, 2021 at 04:57:16PM +0400, Abdulla Al Kathiri wrote:
>
>> def insort_right(a, x, lo=0, hi={len(a)}, *, key=None): …
>
> That's a
Oops I forgot that this could evaluate to a set if “a” was defined beforehand.
Maybe not a good idea after all. It’s not a good idea to use a mutable object
anyways a default value.
> On 24 Oct 2021, at 4:57 PM, Abdulla Al Kathiri
> wrote:
>
> How about this syntax:
>
> def insort_right(a, x
On Sun, Oct 24, 2021 at 04:57:16PM +0400, Abdulla Al Kathiri wrote:
> def insort_right(a, x, lo=0, hi={len(a)}, *, key=None): …
That's already legal syntax for a default value of a set with one
element, len(a).
--
Steve
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Python-ideas mailing lis
On Sun, Oct 24, 2021 at 10:18:52PM +1100, Steven D'Aprano wrote:
> Find some languages (Lisp, Smalltalk, any others?) and show that they
> are abused by people in that community.
Oops, sorry I left out a clause.
Find some language **with late-binding defaults** and show that they are
abused by
How about this syntax:
def insort_right(a, x, lo=0, hi={len(a)}, *, key=None): …
Similar to the expression curly brackets in f-string. If the user didn’t
specify a value for hi, the expression between the curly brackets will be
evaluated and assigned to hi.
Abdulla
Sent from my iPhone
> O
On Sun, Oct 24, 2021 at 11:45 PM Ricky Teachey wrote:
>
> It seems to me that the syntax for late binding could be chosen so as to
> leave the possibility of expansion open in the future, and defer (har har)
> the entire generalized thunk discussion?
>
> So why not go with syntax like this, wher
It seems to me that the syntax for late binding could be chosen so as to
leave the possibility of expansion open in the future, and defer (har har)
the entire generalized thunk discussion?
So why not go with syntax like this, where before the ? just represents a
keyword to be bike shedded ("defer"
On Sun, Oct 24, 2021 at 9:52 PM Serhiy Storchaka wrote:
>
> 23.10.21 19:07, Chris Angelico пише:
> > _missing = object()
> > def spaminate(thing, count=_missing):
> > if count is _missing: count = thing.getdefault()
> >
> > Proposal: Proper syntax and support for late-bound argument defaults.
On Sat, Oct 23, 2021 at 11:47:59PM -0700, Brendan Barnwell wrote:
> It's true that any feature can be abused, but I think this
> temptation to shoehorn function logic into the argument list will be
> more
> likely to result in unwieldy signatures than the current situation.
That sh
23.10.21 19:07, Chris Angelico пише:
> _missing = object()
> def spaminate(thing, count=_missing):
> if count is _missing: count = thing.getdefault()
>
> Proposal: Proper syntax and support for late-bound argument defaults.
>
> def spaminate(thing, count=:thing.getdefault()):
> ...
Few y
On 2021-10-23 23:33, Steven D'Aprano wrote:
On Sat, Oct 23, 2021 at 08:29:54PM -0700, Brendan Barnwell wrote:
For me the biggest problem with this idea is that it only handles a
subset of cases, namely those that can be expressed as an expression
inlined into the function definition.
On Sat, Oct 23, 2021 at 11:53 PM Steven D'Aprano
wrote:
> If we had thunks, that would give us late binding for free:
>
> def bisect(a, x, lo=0, hi=thunk len(a), *, key=None)
>
I'm unclear on exactly what the semantics of a thunk would be, but I don't
see how it could do what you want here.
On Sun, Oct 24, 2021 at 5:53 PM Steven D'Aprano wrote:
>
> On Sun, Oct 24, 2021 at 02:09:59PM +1100, Chris Angelico wrote:
>
> > The biggest problem with thunks is knowing when to trigger evaluation.
>
> I think Algol solved that problem by having thunks a purely internal
> mechanism, not a first-
On Sun, Oct 24, 2021 at 02:09:59PM +1100, Chris Angelico wrote:
> The biggest problem with thunks is knowing when to trigger evaluation.
I think Algol solved that problem by having thunks a purely internal
mechanism, not a first-class value that users could store or pass
around.
> We already
On Sat, Oct 23, 2021 at 08:29:54PM -0700, Brendan Barnwell wrote:
> For me the biggest problem with this idea is that it only handles a
> subset of cases, namely those that can be expressed as an expression
> inlined into the function definition.
True. But that's equally true for default va
On Sun, Oct 24, 2021 at 3:51 PM Brendan Barnwell wrote:
>
> On 2021-10-23 09:07, Chris Angelico wrote:
> > Proposal: Proper syntax and support for late-bound argument defaults.
> >
> > def spaminate(thing, count=:thing.getdefault()):
> > ...
>
> I'm -1 on it.
>
> For me the bi
On 2021-10-23 09:07, Chris Angelico wrote:
Proposal: Proper syntax and support for late-bound argument defaults.
def spaminate(thing, count=:thing.getdefault()):
...
I'm -1 on it.
For me the biggest problem with this idea is that it only handles a
subset of cases, namely
On 2021-10-24 at 13:23:51 +1100,
Steven D'Aprano wrote:
> On Sat, Oct 23, 2021 at 02:54:54PM -0700, 2qdxy4rzwzuui...@potatochowder.com
> wrote:
>
> [...]
> > > The function header is a syntactic construct - the "def" line, any
> > > decorators, annotations, etc.
> >
> > If you mean that def st
On Sun, Oct 24, 2021 at 1:53 PM Steven D'Aprano wrote:
>
> On Sun, Oct 24, 2021 at 01:16:02PM +1100, Chris Angelico wrote:
>
> > What I'm more often seeing is cases that are less obviously a
> > late-binding, but where the sentinel is replaced with the "real" value
> > at the point where it's used
On Sat, Oct 23, 2021 at 7:55 PM Steven D'Aprano wrote:
>
> And is it really a problem if we delay the late-binding to the point
> where the value is actually needed? ...
[in that csse] I would stick to manual late-
> binding using None, and only evaluate it as needed.
>
> Maybe this i
--- Bruce
On Sat, Oct 23, 2021 at 7:55 PM Chris Angelico wrote:
> On Sun, Oct 24, 2021 at 1:48 PM Bruce Leban wrote:
> >
> >
> > On Sat, Oct 23, 2021 at 6:23 PM Jelle Zijlstra
> wrote:
> >>
> >> In the PEP's example:
> >>
> >> def bisect_right(a, x, lo=0, hi=>len(a), *, key=None):
> >>
> >>
On Sat, Oct 23, 2021 at 7:00 PM Steven D'Aprano wrote:
> I challenge that assertion. I've never knowingly seen a function where
> the late binding is "buried deeper in the function", certainly not deep
> enough that it is not obvious. It is a very strong convention that such
> late binding operat
On Sun, Oct 24, 2021 at 01:16:02PM +1100, Chris Angelico wrote:
> What I'm more often seeing is cases that are less obviously a
> late-binding, but where the sentinel is replaced with the "real" value
> at the point where it's used, rather than up the top of the function.
Got any examples you can
On Sun, Oct 24, 2021 at 1:48 PM Bruce Leban wrote:
>
>
> On Sat, Oct 23, 2021 at 6:23 PM Jelle Zijlstra
> wrote:
>>
>> In the PEP's example:
>>
>> def bisect_right(a, x, lo=0, hi=>len(a), *, key=None):
>>
>> This reads to me like we're putting "hi" into "len(a)", when it's in fact
>> the revers
On Sat, Oct 23, 2021 at 6:23 PM Jelle Zijlstra
wrote:
> In the PEP's example:
>
> def bisect_right(a, x, lo=0, hi=>len(a), *, key=None):
>
> This reads to me like we're putting "hi" into "len(a)", when it's in fact
> the reverse.
>
I think in most cases what's on the right side will be something
On Sat, Oct 23, 2021 at 02:54:54PM -0700, 2qdxy4rzwzuui...@potatochowder.com
wrote:
[...]
> > The function header is a syntactic construct - the "def" line, any
> > decorators, annotations, etc.
>
> If you mean that def statements and decorators run at compile time, then
> I agree. If you mean
On Sun, Oct 24, 2021 at 1:12 PM Ricky Teachey wrote:
>
> This might be a dumb question but is the context built only left to right? Or
> will this be legal?
>
> def f(a, *, b=:c, c=:b):
> print(f"{a=} {b=} {c=}")
>
> >>> f(1, b=2)
> a=1 b=2 c=2
>
> >>> f(1, c=2)
> a=1 b=2 c=2
>
That's someth
On Sun, Oct 24, 2021 at 1:00 PM Steven D'Aprano wrote:
>
> On Sun, Oct 24, 2021 at 06:54:36AM +1100, Chris Angelico wrote:
>
> [...]
> > Teaching moment. Currently, the equivalent second function would be this:
> >
> > def f2(l=None):
> > if l is None: l = []
> > l.append(4)
> > return
This might be a dumb question but is the context built only left to right?
Or will this be legal?
def f(a, *, b=:c, c=:b):
print(f"{a=} {b=} {c=}")
>>> f(1, b=2)
a=1 b=2 c=2
>>> f(1, c=2)
a=1 b=2 c=2
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Python-ideas mailing list -- python-ideas@py
On Sun, Oct 24, 2021 at 12:44 PM Rob Cliffe wrote:
> I'm not keen on the
> var = > expr
> syntax. IMO the arrow is pointing the wrong way. expr is assigned to var.
That's definitely open to discussion.
> Some possible alternatives, if there is no technical reason they
> wouldn't work (as
On Sun, Oct 24, 2021 at 06:54:36AM +1100, Chris Angelico wrote:
[...]
> Teaching moment. Currently, the equivalent second function would be this:
>
> def f2(l=None):
> if l is None: l = []
> l.append(4)
> return l
>
> And the whole "early bind or late bind" question is there just the
El sáb, 23 oct 2021 a las 12:57, Guido van Rossum ()
escribió:
> I like that you're trying to fix this wart! I think that using a different
> syntax may be the only way out. My own bikeshed color to try would be `=>`,
> assuming we'll introduce `(x) => x+1` as the new lambda syntax, but I can
> se
On Sun, Oct 24, 2021 at 9:05 AM Ethan Furman wrote:
>
> On 10/23/21 2:23 PM, Chris Angelico wrote:
>
> > It seems like there's broad interest in this, but a lot of details to
> > nut out. I think it may be time for me to write up a full PEP. Guido,
> > if I'm understanding recent SC decisions c
On Sun, Oct 24, 2021 at 8:56 AM <2qdxy4rzwzuui...@potatochowder.com> wrote:
>
> On 2021-10-24 at 06:54:36 +1100,
> Chris Angelico wrote:
>
> > On Sun, Oct 24, 2021 at 6:18 AM <2qdxy4rzwzuui...@potatochowder.com> wrote:
> > > > The expression would be evaluated in the function's context, having
> >
On 10/23/21 2:23 PM, Chris Angelico wrote:
> It seems like there's broad interest in this, but a lot of details to
> nut out. I think it may be time for me to write up a full PEP. Guido,
> if I'm understanding recent SC decisions correctly, a PEP editor can
> self-sponsor, correct?
Of all people
On 2021-10-24 at 06:54:36 +1100,
Chris Angelico wrote:
> On Sun, Oct 24, 2021 at 6:18 AM <2qdxy4rzwzuui...@potatochowder.com> wrote:
> > > The expression would be evaluated in the function's context, having
> > > available to it everything that the function has. Notably, this is NOT
> > > the sam
On Sun, Oct 24, 2021 at 7:58 AM Bruce Leban wrote:
>
> On Sat, Oct 23, 2021 at 12:56 PM Guido van Rossum wrote:
>>
>> I like that you're trying to fix this wart! I think that using a different
>> syntax may be the only way out. My own bikeshed color to try would be `=>`,
>> assuming we'll intro
On Sun, Oct 24, 2021 at 6:55 AM Guido van Rossum wrote:
>
> I like that you're trying to fix this wart! I think that using a different
> syntax may be the only way out. My own bikeshed color to try would be `=>`,
> assuming we'll introduce `(x) => x+1` as the new lambda syntax, but I can see
>
On Sat, Oct 23, 2021 at 12:56 PM Guido van Rossum wrote:
> I like that you're trying to fix this wart! I think that using a different
> syntax may be the only way out. My own bikeshed color to try would be `=>`,
> assuming we'll introduce `(x) => x+1` as the new lambda syntax, but I can
> see pro
On Sat, 23 Oct 2021 at 17:09, Chris Angelico wrote:
>
> Proposal: Proper syntax and support for late-bound argument defaults.
>
> def spaminate(thing, count=:thing.getdefault()):
> ...
>
> def bisect(a, x, lo=0, hi=:len(a)):
> if lo < 0:
> raise ValueError('lo must be non-negative'
On Sun, Oct 24, 2021 at 6:18 AM <2qdxy4rzwzuui...@potatochowder.com> wrote:
> > The expression would be evaluated in the function's context, having
> > available to it everything that the function has. Notably, this is NOT
> > the same as the context of the function definition, but this is only
> >
I like that you're trying to fix this wart! I think that using a different
syntax may be the only way out. My own bikeshed color to try would be `=>`,
assuming we'll introduce `(x) => x+1` as the new lambda syntax, but I can
see problems with both as well :-).
--
--Guido van Rossum (python.org/~g
On 2021-10-24 at 03:07:45 +1100,
Chris Angelico wrote:
> def bisect(a, x, lo=0, hi=None):
> if lo < 0:
> raise ValueError('lo must be non-negative')
> if hi is None:
> hi = len(a)
>
> It's clear what value lo gets if you omit it. It's less clear what hi
> gets. And the si
On Sun, Oct 24, 2021 at 4:12 AM Ethan Furman wrote:
>
> On 10/23/21 9:44 AM, Chris Angelico wrote:
>
> > Feel free to propose an improvement to the syntax. Whatever spelling
> > is ultimately used, this would still be of value.
>
> def bisect(a, x, lo=0, hi?=len(a)):
>
Ah, okay. I had cons
On 10/23/21 9:44 AM, Chris Angelico wrote:
> Feel free to propose an improvement to the syntax. Whatever spelling
> is ultimately used, this would still be of value.
def bisect(a, x, lo=0, hi?=len(a)):
--
~Ethan~
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On Sun, Oct 24, 2021 at 3:26 AM Ethan Furman wrote:
>
> On 10/23/21 9:07 AM, Chris Angelico wrote:
>
> > Proposal: Proper syntax and support for late-bound argument defaults.
>
> I like the proposal.
>
> > def spaminate(thing, count=:thing.getdefault()):
> > ...
> >
> > def bisect(a, x,
On 10/23/21 9:07 AM, Chris Angelico wrote:
> Proposal: Proper syntax and support for late-bound argument defaults.
I like the proposal.
> def spaminate(thing, count=:thing.getdefault()):
> ...
>
> def bisect(a, x, lo=0, hi=:len(a)):
> if lo < 0:
> raise ValueError('lo must be
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