tobiah wrote: >>>Posted via a free Usenet account from http://www.teranews.com >> >>Its all about context. If you want to match something but only if it >>precedes something else, then you follow the regular expression for >>'something' by the regular expression for 'something else' where >>`something else` is enclosed by (?=...) >> >>The regular expression engine will surreptitiously check that >>'something else' does indeed follow, before returning any match of >>'something'. > > > > How would this differ from just > > re.search('somethingsomething else') > The difference is only significant if your pattern contains groups that should be available after the match is complete, or if the match is folloed by further match elements. A lookahead assertion does precisely that: it looks past the current cursor position and allows an assertion about the contents, but without moving the cursor position.
regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://holdenweb.blogspot.com Recent Ramblings http://del.icio.us/steve.holden -- http://mail.python.org/mailman/listinfo/python-list
