[Python-3000] optimizing [x]range (original) (raw)

Guido van Rossum guido at python.org
Sun Jul 29 19:37:53 CEST 2007

On 7/29/07, tomer filiba <tomerfiliba at gmail.com> wrote:

i understand there is no much need for using ranges instead of intervals (a < x < b), but:

1) it's already supported. you CAN use x in range(100), so why not optimize it? there's no justification to keep it an O(N) operation (you're not trying to punish anyone :). it just calls for adding a contains slot to range objects. the cost is very minimal.

Don't forget the cost in terms of code bloat. Plus, I asked for a patch. Where is it? This is not Santa Claus's email address. You're expected to contribute more than a wish.

2) ranges are more like set-builder notation, i.e. evens = {2*n | n in N} which can be written as evens = range(0, maxint, 2) odds = range(1, maxint, 2) you cannot phrase "x in odds" in "a <= x < b" notation. sure, just use modulu, but then it just gets ugly.

Um, your range "solution" would break for examples like 2**100 in evens (it's hard to think of a more even number than that. :-)

Typically one would write a predicate that tested for modulo.

if range (== xrange) would be a cheap, O(1) operation, there's not reason to to use it when it suits well.

But I still see no reason to make it O(1).

-tomer

On Jul 29, 12:04 am, "Guido van Rossum" <gu... at python.org> wrote: > Do we really need another way to spell a <= x < b? Have you got a_ _> real-world use case in mind for the version with step > 1? > > I'm at most lukewarm; I'd be willing to look at a patch to the C code > in the py3k-struni branch, plus unit tests though. > > --Guido >

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-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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