Regex that matches path, filename and extension

I was looking for a regular expression for Python capable to match a string containing a valid path, filename and extension. Finally, I discovered following solution:

^(.*/)?(?:$|(.+?)(?:(\.[^.]*$)|$))

Let me explain how I got this regular expression. Fortunately, Scott Carpenter has written an excellent article about a regular expression to match a filename with extension. Matching the filename extension is not trivial for all possible situations.