Attached is a three-line script whose third line, a call to match() for a compiled regex, fails to halt on Python 2.7 and on 3.4 (after changing ur in front of the regex string to r to accommodate the change in Unicode handling).  I found it by stepping through the debugger so I suspect the problem is in the C backend, not the Python.

Minimal example for your case is

re.match(r'(\w+\s*)+\s+\d+', 'Compiling Regular Patterns to Sequential Machines')

It doesn't halt, it just needs too long time to finish. Your should rewrite the regular expression to avoid catastrophic backtracking (http://www.regular-expressions.info/catastrophic.html). For example rewrite the start of your expression as

re.match(r'\w[\w\s]*\s\d+', 'Compiling Regular Patterns to Sequential Machines')

The problem is with the "(\w+\s*)+". \s* can match an empty string, so when matching a word it's like "(\w+)+".

If you have n letters, there are 2**n ways it could match, and if what follows never matches, it'll try all of them.

It _will_ finish, eventually...