generator expressions: performance anomaly?

[Steve Holden]

Paul Rubin wrote:

> Steve Holden <steve at holdenweb.com> writes:
> 
>>You probably already know that sensible compiled language systems have
>>used constant folding since time immemorial, but Python has always
>>eschewed it. That's what comes of being a pragmatist's language: if
>>such optimizations really are required the programmer is expected to
>>perform them.
> 
> 
> You mean the lack is deliberate?  I just figured it was an artifact of
> the implementation and that PyPy had some reasonable chance of fixing it.

No, it's not been deliberately omitted, it's just not a development 
priority. Pragmatic Python programmers are prepared to do the folding 
themselves in the (exceptionally rare) cases where it has a significant 
effect on performance.

PyPy may or may not fix it. And, of course, a dynamic language has 
rather less ability to take advantage of more advanced optimizations 
since it's much harder to guarantee functional behavior for any given 
subexpression. Once side effects rear their ugly heads all bets are off.

regards
  Steve
-- 
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