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Thu Jun 1 04:30:35 CEST 2006 · https://mail.python.org/pipermail/python-dev/2006-June/065502.html

On 5/31/06, Tim Peters <tim.peters at gmail.com> wrote:
> [Fredrik Lundh]
> > would "abc".find("", 100) == 3 be okay?  or should we switch to treating the
> > optional start and end positions as "return value boundaries" (used to filter the
> > result) rather than "slice directives" (used to process the source string before
> > the operation)?  it's all trivial to implement, and has no performance implications,
> > but I'm not sure what the consensus really is...
>
> FWIW, I like what you eventually did:
>
> >>> "ab".find("")
> 0
> >>> "ab".find("", 1)
> 1
> >>> "ab".find("", 2)
> 2
> >>> "ab".find("", 3)
> -1
> >>> "ab".rfind("")
> 2
> >>> "ab".rfind("", 1)
> 2
> >>> "ab".rfind("", 2)
> 2
> >>> "ab".rfind("", 3)
> -1
>
> I don't know that a compelling argument can be made for such a
> seemingly senseless operation, but the behavior above is at least
> consistent with the rule that a string of length n has exactly n+1
> empty substrings, at 0:0, 1:1, ..., and n:n.

Yes. Bravo!

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

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[Python-Dev] Search for empty substrings (was Re: Let's stop eating exceptions in dict lookup)