[Python-Dev] Lukewarm about range literals (original) (raw)

Michael Hudson mwh21@cam.ac.uk
29 Aug 2000 18:34:15 +0100

Skip Montanaro <skip@mojam.com> writes:

One of the original arguments for range literals as I recall was that indexing of loops could get more efficient. The compiler would know that [0💯2] represents a series of integers and could conceivably generate more efficient loop indexing code (and so could Python2C and other compilers that generated C code). This argument doesn't seem to be showing up here at all. Does it carry no weight in the face of the relative inscrutability of the syntax?

IMHO, no. A compiler sufficiently smart to optimize range literals ought to be sufficiently smart to optimize most calls to "range". At least, I think so. I also think the inefficiency of list construction in Python loops is a red herring; executing the list body involves going round & round the eval loop, and I'd be amazed if that didn't dominate (note that - on my system at least - loops involving range are often (marginally) faster than ones using xrange, presumably due to the special casing of list[integer] in eval_code2).

Sure, it would be nice is this aspect got optimized, but lets speed up the rest of the interpreter enough so you can notice first!

Cheers, Michael

-- Very rough; like estimating the productivity of a welder by the amount of acetylene used. -- Paul Svensson, comp.lang.python [on the subject of the measuring programmer productivity by LOC]