On Fri, Dec 16, 2011 at 10:36 AM, MRAB <pyt...@mrabarnett.plus.com> wrote: > On 16/12/2011 16:49, John Gordon 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. >> > How about this: > > result = re.sub(r"\b0+(\d)\b", r"\1", string)
Close. pattern = r'\b0+([1-9a-f]+|0)\b' re.sub(pattern, r'\1', string, flags=re.IGNORECASE) Cheers, Ian -- http://mail.python.org/mailman/listinfo/python-list
