Philippe Verdy <verd...@wanadoo.fr> added the comment: Rationale for the compilation flag:
You could think that the compilation flag should not be needed. However, not using it would mean that a LOT of existing regular expressions that already contain capturing groups in repetitions, and for which the caputiring group is effectively not used and should have been better encoded as a non-capuring group like (?:X) instead of (X), will suffer a negative performance impact and a higher memory usage. The reason is that the MatchObject will have to store lists of (start,end) pairs instead of just a single pair: using a list will not be the default, so MatchObject.group(groupIndex), MatchObject.start(groupIndex), MatchObject.end(groupIndex), and MatchObject.span(groupIndex) will continue to return a single value or single pair, when the R compilation flag is not set (these values will continue to return only the last occurence, that will be overriden after each matched occurence of the capturing group. The MatchObject.groups() will also continue to return a list of single strings without that flag set (i.e. a list of the last occurence of each capturing group). But when the R flag will be specified, it will return, instead, a list of lists, each element being for the group with the same index and being itself a list of strings, one for each occurence of the capturing group. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue7132> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
