I'd like to see a regexp.exact() method on regexp objects, equivalent to regexp.search(r'\A%s\Z' % pattern, ...), for parsing binary formats.

It's probably not worth disturbing the current library interface for, but maybe in Py3k?

Moving to the feature requests tracker.

Notice that in Py3k, the string type will be a Unicode type, so it's not clear to me that regular expressions on binary data will still be supported.

Binary format searches should be supported once issue 1282 is implemented, 
likely as part of issue 2636 Item 32.  That said, I'm not clear what you 
mean by exact search; wouldn't you want match instead?  If your main issue 
is you want something that automatically binds to the beginning and ending 
of input, then I suppose we could add an 'exact' method where 'search' 
searches anywhere, 'match' matches from the start of input and 'exact' 
matches from beginning to ending.  I'd call that a separate issue, though.  
In other words: byte-oriented matches is covered by 1282 and adding an 
'exact' method is the only new issue here.  Does that sound right?

Yes, that's right. The binary aspect of it was something of a red
herring, I'm afraid, although I still think that (or parsing in general)
is an important use case. The prime motivation it that it's easy to
either forget the '\Z' or to use '$' instead, which both cause subtle
bugs. An exact() method might help to avoid that.