I can recommend Mastering Regular Expressions by Jeffrey Friedl. He goes into great detail on regexp performance and the reason various expressions are slow.
I picked up an older revision from abebooks or ebay. The Python 2.7 online docs recommend revision 1 and states later revs don't cover Python.
I picked up an older revision from abebooks or ebay. The Python 2.7 online docs recommend revision 1 and states later revs don't cover Python.