On 2006-09-07, Paddy <[EMAIL PROTECTED]> wrote: > tobiah wrote: >> (?=...) >> Positive lookahead assertion. This succeeds if the contained >> regular expression, represented here by ..., successfully >> matches at the current location, and fails otherwise. But, >> once the contained expression has been tried, the matching >> engine doesn't advance at all; the rest of the pattern is >> tried right where the assertion started. >> >> I am unable to wrap my mind around this sentence. Could >> someone give me an example of how this works, and why it would >> be useful? > > 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'.
At any rate it further blurs the line between parsing and pattern-matching. ;) -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
