The result '\\&' is only displayed - actually the string is \&:

Copy>>> str = '&'
>>> new_str = str.replace('&', '\&')
>>> new_str
'\\&'
>>> print new_str
\&

Try it in a shell.

To answer your question directly, put r in front of the string.

final= path + r'\xulrunner.exe ' + path + r'\application.ini'

More on Python's site here

Both string and bytes literals may optionally be prefixed with a letter 'r' or 'R'; such strings are called raw strings and treat backslashes as literal characters

But a better solution would be os.path.join:

final = (os.path.join(path, 'xulrunner.exe') + ' ' +
         os.path.join(path, 'application.ini'))

(I split this across two lines for readability, but you could put the whole thing on one line if you want.)

I will mention that you can use forward slashes in file paths, and Python will automatically convert them to the correct separator (backslash on Windows) as necessary. So

final = path + '/xulrunner.exe ' + path + '/application.ini'

should work. But it's still preferable to use os.path.join because that makes it clear what you're trying to do.

So there are a few escape sequences to be aware of in python and they are mainly these.

So when the string for that file location is parsed by the add_argument method it may not be interpreted as a raw string like you've declared and there will be no way to escape the backslashes outside of the declaration.

What you can do instead is to keep it as a regular string (removing the 'r' prefix from the string) and using the escape character for a backslash in any places there may be conflict with another escape character (in this case \t). This may work as the method may evaluate the string correctly.

Try declaring your string like this.

foo = "C:\Users\\test.doc"

Hopefully this helps fix your issue!

EDIT:

In response to handling the dynamic file location you could maybe do something like the following!

def clean(s):
    s = s.replace("\t", "\\t")
    s = s.replace("\n", "\\n")
    return s

Until you've covered all of your bases with what locations you may need to work with! This solution might be more appropriate for your needs. It's kind of funny I didn't think of doing it this way before. Hopefully this helps!