[Python-Dev] Remove str.find in 3.0?
jcarlson at uci.edu
Wed Aug 31 07:30:58 CEST 2005
Steve Holden <steve at holdenweb.com> wrote:
> Guido van Rossum wrote:
> > On 8/30/05, Andrew Durdin <adurdin at gmail.com> wrote:
> > Hm. The example is poorly chosen because it's an end case. The
> > invariant for both is (I'd hope!)
> > "".join(s.partition()) == s == "".join(s.rpartition())
> > Thus,
> > "a/b/c".partition("/") returns ("a", "/", "b/c")
> > "a/b/c".rpartition("/") returns ("a/b", "/", "c")
> > That can't be confusing can it?
> > (Just think of it as rpartition() stopping at the last occurrence,
> > rather than searching from the right. :-)
> So we can check that a substring x appears precisely once in the string
> s using
> s.partition(x) == s.rpartition(x)
> Oops, it fails if s == "". I can usually find some way to go wrong ...
There was an example in the standard library that used "s.find(y) ==
s.rfind(y)" as a test for zero or 1 instances of the searched for item.
Generally though, s.count(x)==1 is a better test.
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