[Python-Dev] (name := expression) doesn't fit the narrative of PEP 20

[Guido van Rossum]

On Wed, Apr 25, 2018 at 1:55 PM, Łukasz Langa <lukasz at langa.pl> wrote:

>
> > On 25 Apr, 2018, at 1:28 PM, Guido van Rossum <guido at python.org> wrote:
> >
> > You don't seem to grasp the usability improvements this will give. I
> hear you but at this point appeals to Python's "Zen" don't help you.
>
> This reads dismissive to me. I did read the PEP and followed the
> discussion on
> python-dev.


It was meant dismissive. With Chris, I am tired of every core dev starting
their own thread about how PEP 572 threatens readability or doesn't reach
the bar for new syntax (etc.). These arguments are entirely emotional and
subjective.

And that's how big decisions get made. Nobody can predict the outcome with
sufficient accuracy. It's like buying a new car or house. In the end you
decide with your gut.


> I referred to PEP 20 because it distills what's unique about the
> value proposition of Python. It's our shared vocabulary.
>

It's poetry, not a set of axioms. You can't *prove* anything with an appeal
to PEP 20. You can appeal to it, for sure, but such an appeal *by
definition* is subjective and emotional. (There's Only One Way To Do It?
Give me a break. :-)


> Can you address the specific criticism I had? To paraphrase it without PEP
> 20
> jargon:
>
> > (name := expression) makes code less uniform.  It inserts more
> information
> > into a place that is already heavily packed with information (logic
> tests).
>

Most Python features make code less uniform in order to make it less
repetitive. (Who needs classes? :-)

-- 
--Guido van Rossum (python.org/~guido)
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