[Python-Dev] PEP 572: Assignment Expressions (original) (raw)

Steve Holden steve at holdenweb.com
Tue Apr 24 07:37:06 EDT 2018

What facilities does the interpreter currently have for extracting common subexpressions, and how would it verify in such a dynamic environment that such extractions wouldn't alter the semantics of the program? Explicit (assignment using :=) is better than implicit (by optimizations hidden to the programmer).

regards Steve

Steve Holden

On Mon, Apr 23, 2018 at 6:13 PM, 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 - xbase if diff and gcd(diff, n) > 1: return gcd(diff, n) # or if (x - xbase) and gcd(x - xbase, n) > 1: return gcd(x - xbase, n)

and have the interpreter handle the optimization, or apply an lrucache? ;-) Cheers, Sven

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