Should be a simple matter of modifying the
Code:
(?P<series_index>[0-9]*)
section to say that the character set should include a period in addition to numbers.
So:
Code:
(?P<series_index>[.0-9]*)
...
AFAIK the period shouldn't do anything wonky re: filenames, unless of course the file has no extension -- which would mean the period there was declaring everything else to be the file extension.

Fortunately, that is rather unlikely.