Regular expression to match a #

[Devan L]

John Machin wrote:
> Aahz wrote:
> > In article <42fb45d7$1 at news.eftel.com>,
> > John Machin  <sjmachin at lexicon.net> wrote:
> >
> >>Search for r'^something' can never be better/faster than match for
> >>r'something', and with a dopey implementation of search [which Python's
> >>re is NOT] it could be much worse. So please don't tell newbies to
> >>search for r'^something'.
> >
> >
> > You're somehow getting mixed up in thinking that "^" is some kind of
> > "not" operator -- it's the start of line anchor in this context.
>
> I can't imagine where you got that idea from.
>
> If I change "[which Python's re is NOT]" to "[Python's re's search() is
> not dopey]", does that help you?
>
> The point was made in a context where the OP appeared to be reading a
> line at a time and parsing it, and re.compile(r'something').match()
> would do the job; re.compile(r'^something').search() will do the job too
> -- BECAUSE ^ means start of line anchor -- but somewhat redundantly, and
> very inefficiently in the failing case with dopey implementations of
> search() (which apply match() at offsets 0, 1, 2, .....).

I don't see much difference.
Python 2.4.1 (#65, Mar 30 2005, 09:13:57) [MSC v.1310 32 bit (Intel)]
on win32
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IDLE 1.1.1
>>> import timeit
>>> t1 = timeit.Timer('re.search("^\w"," will not work")','import re')
>>> t1.timeit()
34.938577109660628
>>> t2 = timeit.Timer('re.match("\w"," will not work")','import re')
>>> t2.timeit()
31.381461330979164
>>> 3.0/1000000
3.0000000000000001e-006
>>> t1.timeit()
35.282282524734228
>>> t2.timeit()
31.403153752781463

~4 second difference after a million times through seems to be trivial.
Then again, I haven't tested it for larger patterns and strings.