Equivalent of Perl chomp?
sholden at holdenweb.com
Tue Feb 5 00:27:20 CET 2002
"Tim Peters" <tim.one at home.com> wrote in message
news:mailman.1012626605.22240.python-list at python.org...
> [Steve Holden]
[times variations of slicing and dicing strings]
> This is the kind of fun I was hoping the OP would have. Good job! A
> to take is that timing even seemingly trivial things can turn up major
> surprises with seemingly trivial changes in exactly what it is you're
> timing. The results are almost never accidental, but determining the true
> causes can leave you crawling on your belly for weeks begging for relief.
Yup. Real life can always sock you in the eye.
> A few things going on in this test under the covers:
> + endswith does indeed pay a large price for building a bound
> method object every time. It's not only the dict lookup to
> resolve "endswith", but also malloc and free to build the
> bound method object and discard it afterwards.
Hmm, I seem to remember someone else spotted that, not me.
> + The huge increase in sliceit's time going from 1 to 2 is due to
> that s[:-1] creates a one-character string, and Python interns
> those by magic: every instance of, e.g., 'a', no matter how
> computed, is exactly the same object (that's not actually true,
> but it's close <wink>). But 2-character computed strings are
> not interned, so s[:-2] has to malloc a fresh string object each
> time to hold the two characters, and free it later. endswith
> doesn't have to build new string objects, so doesn't care as much.
I'd more or less got there.
> Now for some real fun: I have no idea why endswith took a huge jump going
> from 1 to 2. The saving grace for me is that it's so easy to find timing
> mysteries that I'd go mad if I felt compelled to chase them all down, so I
> can walk away without even looking back. I hope not everyone is so
> well-adjusted <wink>, though, as I'd like to know why.
> like-living-in-pumpkin-ly y'rs - tim
Being as well-adjusted (?!) as you, I am happy to see that Bengt is
sufficiently anal to take up the cudgels and "chomp this one to death".
we-can't-all-be-well-adjusted-ly y'rs - steve
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