Nick Coghlan wrote:
I'd be +0 on an "is=" spelling
But "is=' looks like some kind of comparison
operator. This seems even more conusing to me.
--
Greg
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On 2018-04-24 23:32, Cameron Simpson wrote:
On 24Apr2018 08:51, Ethan Furman wrote:
When I compare to variables from outer scopes they *usually* are on
the *right* side of '=='.
You mean something like
if 2 == x:
? I never write code like that, and I haven't seen it, either.
Just to thi
On 24Apr2018 08:51, Ethan Furman wrote:
When I compare to variables from outer scopes they *usually* are on
the *right* side of '=='.
You mean something like
if 2 == x:
? I never write code like that, and I haven't seen it, either.
Just to this, I also never write code like that but I've
On Tue, Apr 24, 2018 at 10:29:11PM +0100, Anthony Flury via Python-Dev wrote:
> If Python is going to do assignment expressions we shouldn't overload
> parens in my opinion - we should have a separate operator - doing this
> avoids needing to exclude rebinding, and makes such expressions
> cons
On Wed, Apr 25, 2018 at 7:29 AM, Anthony Flury via Python-Dev
wrote:
> On 24/04/18 17:11, Yury Selivanov wrote:
>>
>> On Tue, Apr 24, 2018 at 12:03 PM, Ethan Furman wrote:
>> [..]
>>>
>>> But I do write this:
>>>
>>>def wrapper(func, some_value):
>>> value_I_want = process(some_value)
>>
On 24/04/18 17:11, Yury Selivanov wrote:
On Tue, Apr 24, 2018 at 12:03 PM, Ethan Furman wrote:
[..]
But I do write this:
def wrapper(func, some_value):
value_I_want = process(some_value)
def wrapped(*args, **kwds):
if value_I_want == 42:
...
But this pattern is m
On Apr 24, 2018, at 06:55, Antoine Pitrou wrote:
>
> If the ambition is to find a piece of syntax that reads as "binds",
> then we can use a variation on the FLUFL operator: "<->".
FLUFL Override Approved!
-Barry
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Description: Message signed with OpenPGP
On Wed, Apr 25, 2018 at 2:57 AM, Steven D'Aprano wrote:
> On Wed, Apr 25, 2018 at 02:42:08AM +1000, Chris Angelico wrote:
>
>> > from math import *
>> > process(arg, (pi = 1), pi+1) # allowed
>
>
>> That's not allowed at local scope (at least, it's not allowed at
>> function scope - is th
On Wed, Apr 25, 2018 at 02:42:08AM +1000, Chris Angelico wrote:
> > from math import *
> > process(arg, (pi = 1), pi+1) # allowed
> That's not allowed at local scope (at least, it's not allowed at
> function scope - is there any other "local scope" at which it is
> allowed?).
Of cours
On Wed, Apr 25, 2018 at 2:23 AM, Steven D'Aprano wrote:
> On Tue, Apr 24, 2018 at 11:25:58AM -0400, Yury Selivanov wrote:
>
>> No, it doesn't. The check is performed during compile phase, and
>> Python does not unroll loops. Anyways, read below.
>
> What does unrolling loops have to do with anythi
On Tue, Apr 24, 2018 at 11:35:20AM -0400, Yury Selivanov wrote:
> Yes, it would force users to come up with better names *iff* they want
> to use this new sugar:
>
> if (first_target = get_first_candidate()) ...
> elif (second_target = get_second_candidate()) ...
They're not better names. Ad
On Wed, Apr 25, 2018 at 2:28 AM, Steven D'Aprano wrote:
> On Tue, Apr 24, 2018 at 10:58:24AM -0400, Yury Selivanov wrote:
>
>> Since 'diff' and 'g' must be new names according to rule (3), those
>> who read the code will notice that both were not previously bound.
>
> How am I supposed to notice t
On Tue, Apr 24, 2018 at 11:25:58AM -0400, Yury Selivanov wrote:
> No, it doesn't. The check is performed during compile phase, and
> Python does not unroll loops. Anyways, read below.
What does unrolling loops have to do with anything? And besides, loop
unrolling is an implementation detail -- m
On Tue, Apr 24, 2018 at 10:58:24AM -0400, Yury Selivanov wrote:
> Since 'diff' and 'g' must be new names according to rule (3), those
> who read the code will notice that both were not previously bound.
How am I supposed to notice that they've never been bound without
carefully reading through t
On Tue, Apr 24, 2018 at 12:03 PM, Ethan Furman wrote:
[..]
> But I do write this:
>
> def wrapper(func, some_value):
> value_I_want = process(some_value)
> def wrapped(*args, **kwds):
> if value_I_want == 42:
> ...
But this pattern is more rare than comparing local variab
On Tue, Apr 24, 2018 at 11:58 AM, Chris Angelico wrote:
> On Wed, Apr 25, 2018 at 1:49 AM, Yury Selivanov
> wrote:
>> On Tue, Apr 24, 2018 at 11:34 AM, Steven D'Aprano
>> wrote:
[..]
>>> There's no advantage to using binding-expressions unless you're going to
>>> re-use the name you just defin
On Wed, Apr 25, 2018 at 1:56 AM, Yury Selivanov wrote:
> On Tue, Apr 24, 2018 at 11:51 AM, Ethan Furman wrote:
>
>>> When I compare to variables from outer scopes they *usually* are on
>>> the *right* side of '=='.
>>
>>
>> You mean something like
>>
>> if 2 == x:
>>
>> ? I never write code li
On 04/24/2018 08:56 AM, Yury Selivanov wrote:
On Tue, Apr 24, 2018 at 11:51 AM, Ethan Furman wrote:
When I compare to variables from outer scopes they *usually* are on
the *right* side of '=='.
You mean something like
if 2 == x:
? I never write code like that, and I haven't seen it, e
On Wed, Apr 25, 2018 at 1:49 AM, Yury Selivanov wrote:
> On Tue, Apr 24, 2018 at 11:34 AM, Steven D'Aprano wrote:
>> On Tue, Apr 24, 2018 at 11:05:57AM -0400, Yury Selivanov wrote:
>>
>>> Well, `my_func(a=(b:=foo))` or `my_func(b:=foo)` are also barely
>>> readable to my eye.
>>
>> There's no adv
On Tue, Apr 24, 2018 at 11:51 AM, Ethan Furman wrote:
>> When I compare to variables from outer scopes they *usually* are on
>> the *right* side of '=='.
>
>
> You mean something like
>
> if 2 == x:
>
> ? I never write code like that, and I haven't seen it, either.
Hm. I mean this:
const
On 25 April 2018 at 01:35, Yury Selivanov wrote:
> On Tue, Apr 24, 2018 at 11:31 AM, Nick Coghlan wrote:
>> I *do* think the "no name rebinding except in a while loop header"
>> restriction would be annoying for the if/elif use case and the while
>> use case:
>>
>> while (item = get_item()) i
On Tue, Apr 24, 2018 at 11:34 AM, Steven D'Aprano wrote:
> On Tue, Apr 24, 2018 at 11:05:57AM -0400, Yury Selivanov wrote:
>
>> Well, `my_func(a=(b:=foo))` or `my_func(b:=foo)` are also barely
>> readable to my eye.
>
> There's no advantage to using binding-expressions unless you're going to
> re-
On 04/24/2018 08:35 AM, Yury Selivanov wrote:
Yes, it would force users to come up with better names *iff* they want
to use this new sugar:
if (first_target = get_first_candidate()) ...
elif (second_target = get_second_candidate()) ...
And then the common code below that only cares abou
On 04/24/2018 08:19 AM, Yury Selivanov wrote:
Yes, because I'm trying to think about this from a pragmatic side of
things. My question to myself: "what syntax could I use that would
prevent me from making '=' vs '==' mistake when I code?" To me, the
answer is that I usually want to compare loca
On Tue, Apr 24, 2018 at 11:28 AM, Chris Angelico wrote:
> On re-thinking this, I think the distinction IS possible, but (a) only
> in function/class scope, not at global; and (b) would be defined in
> terms of lexical position, not run-time. For instance:
>
> def f():
> (a = 1) # Legal; 'a' h
On Tue, Apr 24, 2018 at 11:27 AM, Steven D'Aprano wrote:
> On Tue, Apr 24, 2018 at 11:03:35AM -0400, Yury Selivanov wrote:
>
>> My point was that when you see lots of '=' and ':=' used at the
>> statement level, one might try to write "if x = 1" instead of "if x :=
>> 1" -- boom, we have an unexpe
On Tue, Apr 24, 2018 at 11:05:57AM -0400, Yury Selivanov wrote:
> Well, `my_func(a=(b:=foo))` or `my_func(b:=foo)` are also barely
> readable to my eye.
There's no advantage to using binding-expressions unless you're going to
re-use the name you just defined, and that re-use will give you a hint
On Wed, Apr 25, 2018 at 1:15 AM, Steven D'Aprano wrote:
> By the way, the check for existing variables cannot help to be either
> incomplete or incorrect if you try to do it at compile time:
>
>
> from module import *
> (x = 2) # allowed or not allowed?
>
>
> If you don't like wild-card i
On Tue, Apr 24, 2018 at 11:31 AM, Nick Coghlan wrote:
> On 25 April 2018 at 00:54, Eric Snow wrote:
>> Regardless, your 3 rules would benefit either syntax. Nick may have a
>> point that the rules might be an excessive burden, but I don't think
>> it's too big a deal since the restrictions are f
On Tue, Apr 24, 2018 at 11:03:35AM -0400, Yury Selivanov wrote:
> My point was that when you see lots of '=' and ':=' used at the
> statement level, one might try to write "if x = 1" instead of "if x :=
> 1" -- boom, we have an unexpected SyntaxError for some users.
That's a *good* thing. They wi
On Tue, Apr 24, 2018 at 11:15 AM, Steven D'Aprano wrote:
[..]
>> >> 3. Most importantly: it is *not* allowed to mask names in the current
>> >> local scope.
>
> That means you can't rebind existing variables. That means you can't
> rebind to the same variable in a loop.
No, it doesn't. The check
On 25 April 2018 at 00:54, Eric Snow wrote:
> Regardless, your 3 rules would benefit either syntax. Nick may have a
> point that the rules might be an excessive burden, but I don't think
> it's too big a deal since the restrictions are few (and align with the
> most likely usage) and are limited
Yury Selivanov wrote:
> I propose to use the following syntax for assignment expressions:
>
> ( NAME = expr )
Yury, did you notice the subthread [1] that discusses the merits and
problems of the same idea (except for your point 3)?
[1] https://mail.python.org/pipermail/python-dev/2018-April/1
On Tue, Apr 24, 2018 at 11:07 AM, Chris Angelico wrote:
[..]
> x = 1
> if (x = 2): ...
>
> This, according to your proposal, raises SyntaxError - not because a
> comparison was wanted and an assignment was made, but because the name
> already had a value. And, even worse, this is NOT an error:
Y
On Tue, Apr 24, 2018 at 09:50:34AM -0400, Yury Selivanov wrote:
> On Tue, Apr 24, 2018 at 9:46 AM, Nick Coghlan wrote:
> > On 24 April 2018 at 23:38, Yury Selivanov wrote:
> >> I propose to use the following syntax for assignment expressions:
> >>
> >> ( NAME = expr )
> >>
> >> I know that it
On Wed, Apr 25, 2018 at 12:58 AM, Yury Selivanov
wrote:
> On Tue, Apr 24, 2018 at 10:49 AM, Paul Moore wrote:
> [..]
3. Most importantly: it is *not* allowed to mask names in the current
local scope.
>>>
>>> While I agree this would be unambiguous to a computer, I think for
>>> most hum
On Wed, Apr 25, 2018 at 1:03 AM, Yury Selivanov wrote:
> On Tue, Apr 24, 2018 at 10:56 AM, Chris Angelico wrote:
> [..]
>>> A lot of other questions arise though. PEP 572 proposes:
>>>
>>> a = 1 # assignment
>>> a := 1 # also assignment
>>> (a := 1) # also assignment
>>> (a = 1) # error, why
On 24 April 2018 at 15:58, Yury Selivanov wrote:
> On Tue, Apr 24, 2018 at 10:49 AM, Paul Moore wrote:
> [..]
3. Most importantly: it is *not* allowed to mask names in the current
local scope.
>>>
>>> While I agree this would be unambiguous to a computer, I think for
>>> most humans it
On Tue, Apr 24, 2018 at 10:54 AM, Anthony Flury via Python-Dev
wrote:
[..]
> As discussed previously by others on this exact proposals, you now have the
> issue of confusion when using keyword arguments : *my_func(a = b)* :
> clearly that is a call to `my_func' where argument a has the value of b
On Wed, Apr 25, 2018 at 12:54 AM, Anthony Flury via Python-Dev
wrote:
> As discussed previously by others on this exact proposals, you now have the
> issue of confusion when using keyword arguments : *my_func(a = b)* :
> clearly that is a call to `my_func' where argument a has the value of b, but
On Tue, Apr 24, 2018 at 10:49 AM, Paul Moore wrote:
[..]
>>> 3. Most importantly: it is *not* allowed to mask names in the current
>>> local scope.
>>
>> While I agree this would be unambiguous to a computer, I think for
>> most humans it would be experienced as a confusing set of arcane and
>> ar
Thanks for thinking this through, Yury. :)
FWIW, I'm still unconvinced that an assignment expression is worth it.
It's hard to say, though, without seeing how much folks would actually
use it (and I don't have my own time machine unfortunately). IIRC, in
the past several proposed syntax (e.g. dec
On Tue, Apr 24, 2018 at 10:56 AM, Chris Angelico wrote:
[..]
>> A lot of other questions arise though. PEP 572 proposes:
>>
>> a = 1 # assignment
>> a := 1 # also assignment
>> (a := 1) # also assignment
>> (a = 1) # error, why?
>
> Your third example is just the same as the second, with pare
On 24/04/18 14:50, Yury Selivanov wrote:
On Tue, Apr 24, 2018 at 9:46 AM, Nick Coghlan wrote:
On 24 April 2018 at 23:38, Yury Selivanov wrote:
I propose to use the following syntax for assignment expressions:
( NAME = expr )
I know that it was proposed before and this idea was rejected
On Wed, Apr 25, 2018 at 12:23 AM, Yury Selivanov
wrote:
> On Tue, Apr 24, 2018 at 10:07 AM, Nick Coghlan wrote:
>
>>> "=" is always an assignment.
>>> "==" is always an equality check.
>>
>> That's not the distinction I meant, I meant the difficulty of
>> explaining the discrepancies in this list
On 25 April 2018 at 00:23, Yury Selivanov wrote:
> A lot of other questions arise though. PEP 572 proposes:
>
> a = 1 # assignment
> a := 1 # also assignment
> (a := 1) # also assignment
> (a = 1) # error, why?
That's just the typical assignment/expression dichotomy, though, which
is genuine
On 24 April 2018 at 14:46, Nick Coghlan wrote:
> On 24 April 2018 at 23:38, Yury Selivanov wrote:
>> I propose to use the following syntax for assignment expressions:
>>
>> ( NAME = expr )
>>
>> I know that it was proposed before and this idea was rejected, because
>> accidentally using '=' i
On Tue, Apr 24, 2018 at 10:07 AM, Nick Coghlan wrote:
>> "=" is always an assignment.
>> "==" is always an equality check.
>
> That's not the distinction I meant, I meant the difficulty of
> explaining the discrepancies in this list:
>
> a = 1 # Assignment
> (a = 1) # Also assignment
>
> a, b = 1
On 24 April 2018 at 23:50, Yury Selivanov wrote:
> On Tue, Apr 24, 2018 at 9:46 AM, Nick Coghlan wrote:
>> On 24 April 2018 at 23:38, Yury Selivanov wrote:
>>> I propose to use the following syntax for assignment expressions:
>>>
>>> ( NAME = expr )
>>>
>>> I know that it was proposed before
On Tue, 24 Apr 2018 23:46:34 +1000
Nick Coghlan wrote:
> On 24 April 2018 at 23:38, Yury Selivanov wrote:
> > I propose to use the following syntax for assignment expressions:
> >
> > ( NAME = expr )
> >
> > I know that it was proposed before and this idea was rejected, because
> > accidental
On Tue, Apr 24, 2018 at 9:46 AM, Nick Coghlan wrote:
> On 24 April 2018 at 23:38, Yury Selivanov wrote:
>> I propose to use the following syntax for assignment expressions:
>>
>> ( NAME = expr )
>>
>> I know that it was proposed before and this idea was rejected, because
>> accidentally using
On 24 April 2018 at 23:38, Yury Selivanov wrote:
> I propose to use the following syntax for assignment expressions:
>
> ( NAME = expr )
>
> I know that it was proposed before and this idea was rejected, because
> accidentally using '=' in place of '==' is a pain point in
> C/C++/JavaScript.
>
I propose to use the following syntax for assignment expressions:
( NAME = expr )
I know that it was proposed before and this idea was rejected, because
accidentally using '=' in place of '==' is a pain point in
C/C++/JavaScript.
That said, I believe we can still use this syntax as long as w
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