Difference between Python and Javascript in evaluating a regular expression

Question

First of all, this is not a dupe of this question.

In Javascript this expression seems to be evaluated correctly:

\\/(omniture|mbox|hbx|omniunih)(.*)?

If I pass it to Python re module, bad things happen. In fact, the following returns an error:

import re
re.compile (u'\\/(omniture|mbox|hbx|omniunih)(.*)?')

In [101]: re.compile (u'\\/(omniture|mbox|hbx|omniunih)(.*)?')
---------------------------------------------------------------------------
error                                     Traceback (most recent call last)
/home/fakk/spider.io/1/<ipython-input-101-b5b19eb3b66e> in <module>()
----> 1 re.compile (u'\\/(omniture|mbox|hbx|omniunih)(.*)?')

/usr/lib/python2.7/re.pyc in compile(pattern, flags)
    188 def compile(pattern, flags=0):
    189     "Compile a regular expression pattern, returning a pattern object."
--> 190     return _compile(pattern, flags)
    191 
    192 def purge():

/usr/lib/python2.7/re.pyc in _compile(*key)
    242         p = sre_compile.compile(pattern, flags)
    243     except error, v:
--> 244         raise error, v # invalid expression
    245     if len(_cache) >= _MAXCACHE:
    246         _cache.clear()

error: nothing to repeat

Python complains about the (.*)? part, which me myself am not able to understand.

My questions are:

1. What does (.*)? do in JS? Match zero or one (?) of zero or more (*) chars (.)? What's the point?
2. How can I translate it in Python?

Answer 1

The question mark is superfluous, as you reflect yourself, it doesn't really make any sense, remove it and you should be in business.

Answer 2

Your regular expression does not make sense, the ? at the end of your string is not needed and will in fact never match anything. In addition I suggest you use r'' to make your expression easier to read:

import re
my_regex = re.compile(r'\/(omniture|mbox|hbx|omniunih)(.*)')