Steven D'Aprano writes:
> "Write `arg=default` if you want the default to be evaluated just once,
> and `arg=late default` if you want the default to be evaluated each time
> it is needed. If you are not sure which one you need, use the
> first."
Which of course is ambiguous, since the argu
On Wed, Nov 3, 2021 at 6:01 PM Stephen J. Turnbull
wrote:
>
> Steven D'Aprano writes:
>
> > "Write `arg=default` if you want the default to be evaluated just once,
> > and `arg=late default` if you want the default to be evaluated each time
> > it is needed. If you are not sure which one you ne
> But then the question becomes: should we recommend late-binding by
> default, with early-binding as an easy optimization?
Given the decades of code that is using early binding now, I think it would
be a really bad idea not to teach that as the default— folks absolutely
need to understand early
One similarity that I don't think has been mentioned yet:
- decorator syntax says, "run me later, after this function is built"
- late-bound argument syntax says, "run me later, just before each function
call"
Because both mean "run me later" we can leverage the @ symbol to aid understanding;
On 11/2/21 6:03 AM, Florian Wetschoreck wrote:
Hello everyone:
The scenario/observation:
Beginners sometimes create scripts with the name of a package e.g.
pandas.py or seaborn.py in order to test something.
There's a previous discussion about preventing importing a file into
itself. It's a
On Thu, Nov 4, 2021 at 2:29 AM Ethan Furman wrote:
>
> One similarity that I don't think has been mentioned yet:
>
> - decorator syntax says, "run me later, after this function is built"
>
> - late-bound argument syntax says, "run me later, just before each function
> call"
Hmm, I more think of
On 11/3/21 9:07 AM, Chris Angelico wrote:
> On Thu, Nov 4, 2021 at 2:29 AM Ethan Furman wrote:
>> One similarity that I don't think has been mentioned yet:
>>
>> - decorator syntax says, "run me later, after this function is built"
>>
>> - late-bound argument syntax says, "run me later, just befo
On Thu, Nov 04, 2021 at 03:07:22AM +1100, Chris Angelico wrote:
> def func(spam: list = []) -> str: ...
>
> Which part of that becomes late bound?
The name "spam" of course. Without the parameter, nothing gets bound at
all.
> The [], not the name "list", not the name "spam".
The type annotat
On Wed, Nov 03, 2021 at 10:25:02AM -0700, Ethan Furman wrote:
> Which is horrible. Put the @ at the front:
>
> - its relation to decorators, and delayed evaluation, is much more clear
> - it stands out better to the reader
I agree. (Well, I would, wouldn't I? :-)
But if people really, really h
On Thu, Nov 4, 2021 at 4:25 AM Ethan Furman wrote:
>
> On 11/3/21 9:07 AM, Chris Angelico wrote:
> > On Thu, Nov 4, 2021 at 2:29 AM Ethan Furman wrote:
>
> >> One similarity that I don't think has been mentioned yet:
> >>
> >> - decorator syntax says, "run me later, after this function is buil
On Thu, Nov 4, 2021 at 4:30 AM Steven D'Aprano wrote:
>
> On Thu, Nov 04, 2021 at 03:07:22AM +1100, Chris Angelico wrote:
>
> > def func(spam: list = []) -> str: ...
> >
> > Which part of that becomes late bound?
>
> The name "spam" of course. Without the parameter, nothing gets bound at
> all.
T
On Thu, Nov 4, 2021 at 4:38 AM Steven D'Aprano wrote:
>
> On Wed, Nov 03, 2021 at 10:25:02AM -0700, Ethan Furman wrote:
>
> > Which is horrible. Put the @ at the front:
> >
> > - its relation to decorators, and delayed evaluation, is much more clear
> > - it stands out better to the reader
>
> I
On Thu, Nov 04, 2021 at 04:36:27AM +1100, Chris Angelico wrote:
> You use the name because you can't refer to it other than by name, and
> that's fine. But it's the *default* that is different. Not the
> parameter.
Wait, are you saying that the list display here:
parameter=[]
is different f
On Thu, Nov 4, 2021 at 4:56 AM Steven D'Aprano wrote:
>
> On Thu, Nov 04, 2021 at 04:36:27AM +1100, Chris Angelico wrote:
>
> > You use the name because you can't refer to it other than by name, and
> > that's fine. But it's the *default* that is different. Not the
> > parameter.
>
> Wait, are you
On 11/3/21 10:35 AM, Steven D'Aprano wrote:
> I suppose that we could even add yet another overloaded meaning on the
> asterix:
>
> # with no default, * keeps the old meaning of collecting
> # extra positional values
>
> *parameter
>
> # with a default, * triggers late-binding
Chris Angelico writes:
> While it's possible to avoid some of those, we can't hold the
> language back because *someone who doesn't understand* might
> misunderstand.
Opposing the proposal wasn't the point of quoting Steve, the point was
to provide IMO improved language in case the proposal ge
There’s some conflict about whether it’s the name or the expression that’s
different, and thus should be adorned.
But it’s neither: it’s the “=“ that’s different— so that’s what should be a
different symbol.
As for “=>” — I like it now, but if that same symbol is adopted for lambda,
it would be h
On 2021-11-03 18:14, Ethan Furman wrote:
On 11/3/21 10:35 AM, Steven D'Aprano wrote:
> I suppose that we could even add yet another overloaded meaning on the
> asterix:
>
> # with no default, * keeps the old meaning of collecting
> # extra positional values
>
> *para
On 11/3/21 12:13 AM, Chris Angelico wrote:
> Python has a strong policy of evaluating things immediately, or being
> very clear about when they will be evaluated
Putting the marker in the middle of the name binding expression is not "very clear" -- particularly since the advice is
"ne spaces ar
Hey Ned,
Thank you for mentioning the old and related issue.
In order to prevent confusion, I want to point out that the primary
scenario that I meant is not that the file imports itself but another file
in the same directory with the name of a module that is also installed in
site-packages. Not
On 11/3/21 12:21 PM, Florian Wetschoreck wrote:
> In order to prevent confusion, I want to point out that the primary scenario
that I meant is not that the file imports
> itself but another file in the same directory with the name of a module that
is also installed in site-packages. Not
> sure
On Thu, Nov 4, 2021 at 5:28 AM Stephen J. Turnbull
wrote:
>
> > And that's what happens when you need to be pedantically correct. Not
> > particularly useful to a novice, especially with the FUD at the
> > end.
>
> I have no idea what you mean by "that's what happens," except that
> apparently
On Thu, Nov 4, 2021 at 5:54 AM Ethan Furman wrote:
>
> On 11/3/21 12:13 AM, Chris Angelico wrote:
>
> > Python has a strong policy of evaluating things immediately, or being
> > very clear about when they will be evaluated
>
> Putting the marker in the middle of the name binding expression is no
On Thu, Nov 4, 2021 at 6:37 AM Ethan Furman wrote:
>
> On 11/3/21 12:21 PM, Florian Wetschoreck wrote:
>
> > In order to prevent confusion, I want to point out that the primary
> scenario that I meant is not that the file imports
> > itself but another file in the same directory with the name o
On 11/3/21 2:31 PM, Chris Angelico wrote:
> On Thu, Nov 4, 2021 at 5:54 AM Ethan Furman wrote:
>> On 11/3/21 12:13 AM, Chris Angelico wrote:
>>> Python has a strong policy of evaluating things immediately, or being
>>> very clear about when they will be evaluated
>>
>> Putting the marker in the m
On Thu, Nov 4, 2021 at 9:33 AM Ethan Furman wrote:
>
> On 11/3/21 2:31 PM, Chris Angelico wrote:
> > On Thu, Nov 4, 2021 at 5:54 AM Ethan Furman wrote:
> >> On 11/3/21 12:13 AM, Chris Angelico wrote:
>
> >>> Python has a strong policy of evaluating things immediately, or being
> >>> very clear
On 03/11/2021 18:28, Stephen J. Turnbull wrote:
Chris Angelico writes:
> While it's possible to avoid some of those, we can't hold the
> language back because *someone who doesn't understand* might
> misunderstand.
Opposing the proposal wasn't the point of quoting Steve, the point was
t
On Wed, Nov 3, 2021, 9:19 PM Rob Cliffe via Python-ideas
> Some people clearly need it, viz. those who use a default such as `[]` and
> then ask on Stack Overflow why they get surprising results.
This is silly. All those folks on StackOverflow are told "use a sentinel."
The fact beginners can ma
On Thu, Nov 4, 2021 at 12:42 PM David Mertz, Ph.D.
wrote:
> This seems exactly opposite the real situation. Late binding is completely
> and straightforwardly handled by a sentinel. Yes, it doesn't make the
> automatic help() that pretty. Yes it takes an extra line in the body. But the
> semant
On Wed, Nov 3, 2021, 5:41 PM Chris Angelico wrote:
On Thu, Nov 4, 2021 at 6:37 AM Ethan Furman wrote:
>
> On 11/3/21 12:21 PM, Florian Wetschoreck wrote:
>
> > In order to prevent confusion, I want to point out that the primary
scenario that I meant is not that the file imports
> > itself but
On Wed, Nov 3, 2021, 2:40 PM MRAB wrote:
> On 2021-11-03 18:14, Ethan Furman wrote:
> > On 11/3/21 10:35 AM, Steven D'Aprano wrote:
> >
> > > I suppose that we could even add yet another overloaded meaning on
> the
> > > asterix:
> > >
> > > # with no default, * keeps the old meaning
> For example, even though I was only lukewarm in support of the walrus
> operator, I agree it makes a some code constructs more concise and more
> readable. But it WAS new syntax to do the same thing that was already
> possible with an extra line or two before.
>
> It's extra syntax to make a cer
On Thu, Nov 4, 2021 at 3:56 PM Christopher Barker wrote:
> All that being said, like any other PEP, there are two questions:
>
> 1) will this be an improvement?
> 2) if so, is it worth the churn?
>
> And the SC will need to make those decisions.
>
> FWIW, I’m not totally sure where I come down on
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