[Python-Dev] PEP 572: Assignment Expressions

[Chris Angelico]

On Tue, Apr 24, 2018 at 3:13 AM, Sven R. Kunze <srkunze at mail.de> wrote:
> On 23.04.2018 17:59, Steve Holden wrote:
>
>
> While Tim's expression might look (superficially) like C, the five-line
> alternative isn't exactly an inspiring example of Pythonicity, is it?
>
>
> What about
>
> diff = x - x_base
> if diff and gcd(diff, n) > 1:
>     return gcd(diff, n)
>
> # or
>
> if (x - x_base) and gcd(x - x_base, n) > 1:
>     return gcd(x - x_base, n)
>
>
> and have the interpreter handle the optimization, or apply an lru_cache? ;-)

And then you want to change something, and you have to make an edit in
two places. Or, worse, you make it in only one of those places, they
become desynchronized, and nobody can figure out why the program
occasionally and bizarrely fails. Removing duplicate function calls
isn't just about run-time performance.

ChrisA