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

[MRAB]

On 16/12/2011 21:04, John Gordon wrote:
> In<mailman.3737.1324054637.27778.python-list at python.org>  Devin Jeanpierre<jeanpierreda at gmail.com>  writes:
>
>>  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=3Dlambda m: (m.end() =3D m.start()))
>
> I ended up doing something similar:
>
>      # find the longest match
>      longest_match = ''
>      for word in re.findall('((0000:?)+)', ip6):
>          if len(word[0])>  len(longest_match):
>              longest_match = word[0]
>
>      # if we found a match, replace it with a colon
>      if longest_match:
>        ip6 = re.sub(longest_match, ':', ip6, 1)
>
For a simple replace, using re is probably overkill. The .replace
method is a better solution:

ip6 = longest_match.replace(ip6, ':', 1)