Message 83234 - Python tracker

Message83234

Author	mrabarnett
Recipients	effbot, glchapman, mrabarnett
Date	2009-03-06.03:11:24
SpamBayes Score	0.0007615196
Marked as misclassified	No
Message-id	<1236309088.77.0.240637807251.issue814253@psf.upfronthosting.co.za>
In-reply-to

Content
As part of issue #2636 group references now work in lookbehinds. However, your example: (?<=(...)\1)abc will fail but: (?<=\1(...))abc will succeed. Why? Well, in lookbehinds it searches backwards. In the first regex it sees the group reference before the capture, whereas in the second it sees the group reference after the capture. (Hope that's clear! :-))

Content

As part of issue #2636 group references now work in lookbehinds.

However, your example:

    (?<=(...)\1)abc

will fail but:

    (?<=\1(...))abc

will succeed.

Why? Well, in lookbehinds it searches backwards. In the first regex it
sees the group reference before the capture, whereas in the second it
sees the group reference after the capture. (Hope that's clear! :-))

History
Date	User	Action	Args
2009-03-06 03:11:29	mrabarnett	set	recipients: + mrabarnett, effbot, glchapman
2009-03-06 03:11:28	mrabarnett	set	messageid: <1236309088.77.0.240637807251.issue814253@psf.upfronthosting.co.za>
2009-03-06 03:11:25	mrabarnett	link	issue814253 messages
2009-03-06 03:11:24	mrabarnett	create