re.rsearch?

[Christophe Delord]

Hi,

If you compile your pattern, you can give the pattern object a start position and an end position:

>>> p=re.compile("a")
>>> p.search("1a2a").span()
(1, 2)
>>> p.search("1a2a",2).span()
(3, 4)

This may work as you need:

def rsearch(reg, s):
	start, end = None, None
	i = 0
	p = re.compile(reg)
	while 1:
		m = p.search(s, i)
		if m:
			start, end = m.span()
			i = end
		else:
			break
	return start, end


I found this in the documentation at http://web.pydoc.org/2.2/pre.html#RegexObject-search

--
search(self, string, pos=0, endpos=None)
    search(string[, pos][, endpos]) -> MatchObject or None
     
    Scan through string looking for a location where this regular
    expression produces a match, and return a corresponding
    MatchObject instance. Return None if no position in the string
    matches the pattern; note that this is different from finding
    a zero-length match at some point in the string. The optional
    pos and endpos parameters have the same meaning as for the
    match() method.
--

But of course as suggested by Fredrik Lundth, this solution is shorter:

def rsearch(reg, s):
	return re.search("(?:.*)(%s)"%reg, s).span(1)



Best regards,
Christophe.

On 23 Jun 2002 21:42:54 GMT
quinn at baht.ugcs.caltech.edu (Quinn Dunkan) wrote:

> Occaisionally I find myself wanting an re.search that will find the rightmost
> match.  In those occaisions, I use:
> 
> def rsearch(reg, s):
>     'like re.search only find last match, return start, end instead of match'
>     last_m = None
>     start = end = 0
>     while 1:
>         m = re.search(reg, s[end:])
>         if m is None:
>             if last_m is None:
>                 return None, None
>             else:
>                 return start, end
>         last_m = m
>         end += m.end()
>         start = end - (m.end() - m.start())
> 
> ... of course, it would be nicer to return an actual match object, but I
> haven't figured out how to do that short of faking up my own, and I've only
> needed (start, end) so far.  Unfortunately, AFAIK, re.search also lacks a
> 'start_searching_at' type option.
> 
> Has anyone else solved this probem in a more graceful way?


-- 

(o_   Christophe Delord                   _o)
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