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Re: re.sub(): replace longest match instead of leftmost match?

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You could use re.finditer to find the longest match, and then replace
it manually by hand (via string slicing).

(a match is the longest if (m.end() - m.start()) is the largest --
so, max(re.finditer(...), key=lambda m: (m.end() = m.start()))

-- Devin

P.S. does anyone else get bothered by how it's slice.start and
slice.stop, but match.start() and match.end() ?

On Fri, Dec 16, 2011 at 11:49 AM, John Gordon <gordon@panix.com> wrote:
> According to the documentation on re.sub(), it replaces the leftmost
> matching pattern.
>
> However, I want to replace the *longest* matching pattern, which is
> not necessarily the leftmost match.  Any suggestions?
>
> I'm working with IPv6 CIDR strings, and I want to replace the longest
> match of "(0000:|0000$)+" with ":".  But when I use re.sub() it replaces
> the leftmost match, even if there is a longer match later in the string.
>
> I'm also looking for a regexp that will remove leading zeroes in each
> four-digit group, but will leave a single zero if the group was all
> zeroes.
>
> Thanks!
>
> --
> John Gordon                   A is for Amy, who fell down the stairs
> gordon@panix.com              B is for Basil, assaulted by bears
>                                -- Edward Gorey, "The Gashlycrumb Tinies"
>
> --
> http://mail.python.org/mailman/listinfo/python-list

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Thread

re.sub(): replace longest match instead of leftmost match? John Gordon <gordon@panix.com> - 2011-12-16 16:49 +0000
  Re: re.sub(): replace longest match instead of leftmost match? Devin Jeanpierre <jeanpierreda@gmail.com> - 2011-12-16 11:56 -0500
    Re: re.sub(): replace longest match instead of leftmost match? John Gordon <gordon@panix.com> - 2011-12-16 21:04 +0000
      Re: re.sub(): replace longest match instead of leftmost match? MRAB <python@mrabarnett.plus.com> - 2011-12-16 21:36 +0000
        Re: re.sub(): replace longest match instead of leftmost match? Duncan Booth <duncan.booth@invalid.invalid> - 2011-12-19 15:46 +0000
  Re: re.sub(): replace longest match instead of leftmost match? MRAB <python@mrabarnett.plus.com> - 2011-12-16 17:36 +0000
  Re: re.sub(): replace longest match instead of leftmost match? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-16 10:57 -0700
  Re: re.sub(): replace longest match instead of leftmost match? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-16 10:59 -0700
    Re: re.sub(): replace longest match instead of leftmost match? John Gordon <gordon@panix.com> - 2011-12-16 21:06 +0000
  Re: re.sub(): replace longest match instead of leftmost match? MRAB <python@mrabarnett.plus.com> - 2011-12-16 18:19 +0000
  Re: re.sub(): replace longest match instead of leftmost match? Roy Smith <roy@panix.com> - 2011-12-16 13:36 -0500
    Re: re.sub(): replace longest match instead of leftmost match? John Gordon <gordon@panix.com> - 2011-12-16 21:07 +0000
    Re: re.sub(): replace longest match instead of leftmost match? Terry Reedy <tjreedy@udel.edu> - 2011-12-16 17:26 -0500
  Re: re.sub(): replace longest match instead of leftmost match? ting@thsu.org - 2011-12-19 15:15 -0800
    Re: re.sub(): replace longest match instead of leftmost match? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-19 19:58 -0700

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