[Python-Dev] Examples for PEP 572
tim.peters at gmail.com
Wed Jul 4 13:58:39 EDT 2018
> > Sorry, this PEP was rewritten so many times that I missed your
> [Tim's] Appendix.
> >> while total != (total := total + term):
> >> term *= mx2 / (i*(i+1))
> >> i += 2
> >> return total
> > This code looks clever that the original while loop with a break in a
> > middle. I like clever code. But it needs more mental efforts for
> > understanding it.
> > I admit that this is a good example.
> > There is a tiny problem with it (and with rewriting a while loop as a
> > for loop, as I like). Often the body contains not a single break. In
> > this case the large part of cleverness is disappeared. :-(
> It took me a few minutes to figure out that this construct actually
> > checks term == 0.
> > So, this example abuses the construct to do something it's not designed
> > to do: perform an unrelated operation before checking the condition.
> > (Cue attempts to squeeze ever mode code here.) I would fail it in review.
> > This "clever" code is exactly what Perl burned itself on and what
> > Python, being its antithesis, was specifically designed to avoid.
So you didn't read the PEP Appendix at all, and Serhiy did but apparently
skipped reading what the PEP _said_ about that example. It was clearly
identified as abuse: a case in which using assignment expressions made the
code significantly WORSE. I gave examples of both "wins" and "losses"
while staring at real code - I wasn't searching for "proof" that a
pre-determined conclusion was justified.
So I wholly agree with you (Ivan) about that example - and that it struck
Serhiy as a good example convinces me more than before that there's no
overlap in the ways Serhiy and I view this part of the world ;-)
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