[Python-Dev] Re: PEP 622 (Structural Pattern Matching) questions

2020-08-06 Thread Guido van Rossum
On Thu, Aug 6, 2020 at 04:31 Mark Shannon  wrote:

> Hi,
>
> I have two questions about PEP 622, as it stands.
>
> 1. Is the current version the final version?


That is up to the Steering Council.


> 2. Is the difference in semantics between the Django example and the
> proposed replacement deliberate or accidental?
>(The difference being the change in behaviour for sequences other
> than list or tuple).
>
> Cheers,
> Mark.
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[Python-Dev] Re: PEP 622 (Structural Pattern Matching) questions

2020-08-06 Thread Mark Shannon

Hi Daniel,

On 06/08/2020 1:11 pm, Daniel Moisset wrote:

Hi Mark,

As the specific author of that example (and the author of the big it had 
on a previous version) let me clarify:


The change in semantics is intentional. I could be more explicit, and 
preserve semantics, but I actually find very likely that the original 
code does not support other sequences because it would make their code 
more complicated (so it's a matter of opinion but for me it's a feature, 
not a bug)


Are you going to mention in the PEP that the two pieces of code are not 
equivalent, or show an equivalent version?


I don't know whether the original author intended to accept 
`array.array("u", "hi")` as a legal value, but I suspect that they did not.



Cheers,
Mark.



As for the previous fixed bug, of like to mentioned that I misread the 
original code (I tend to use >= rather than > for those comparisons) so 
I read "at least one element" rather than "more than one". Again, it may 
be subjective taste but I find our version more readable in that respect 
and less likely to be misinterpreted (making the bug easier to spot there)


Best,

Daniel



On Thu, 6 Aug 2020, 12:32 Mark Shannon, > wrote:


Hi,

I have two questions about PEP 622, as it stands.

1. Is the current version the final version?

2. Is the difference in semantics between the Django example and the
proposed replacement deliberate or accidental?
    (The difference being the change in behaviour for sequences other
than list or tuple).

Cheers,
Mark.
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[Python-Dev] Re: PEP 622 (Structural Pattern Matching) questions

2020-08-06 Thread Daniel Moisset
Hi Mark,

As the specific author of that example (and the author of the big it had on
a previous version) let me clarify:

The change in semantics is intentional. I could be more explicit, and
preserve semantics, but I actually find very likely that the original code
does not support other sequences because it would make their code more
complicated (so it's a matter of opinion but for me it's a feature, not a
bug)

As for the previous fixed bug, of like to mentioned that I misread the
original code (I tend to use >= rather than > for those comparisons) so I
read "at least one element" rather than "more than one". Again, it may be
subjective taste but I find our version more readable in that respect and
less likely to be misinterpreted (making the bug easier to spot there)

Best,

Daniel



On Thu, 6 Aug 2020, 12:32 Mark Shannon,  wrote:

> Hi,
>
> I have two questions about PEP 622, as it stands.
>
> 1. Is the current version the final version?
>
> 2. Is the difference in semantics between the Django example and the
> proposed replacement deliberate or accidental?
>(The difference being the change in behaviour for sequences other
> than list or tuple).
>
> Cheers,
> Mark.
> ___
> Python-Dev mailing list -- python-dev@python.org
> To unsubscribe send an email to python-dev-le...@python.org
> https://mail.python.org/mailman3/lists/python-dev.python.org/
> Message archived at
> https://mail.python.org/archives/list/python-dev@python.org/message/NQBL4S6WTM5647J2YKJNWM446WX3ELHO/
> Code of Conduct: http://python.org/psf/codeofconduct/
>
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