regex for parsing python printf-style-formatting

printf_regex.py

re.compile("""

%                               # Percent
(?:\((?P<mapping>[^)]*)\))?     # Mapping key
(?P<flag>[#0\-+ ])?             # Conversion Flag
(?P<width>\*|\d+)?              # Field width
(?P<precision>\.(?:\*?|\d*))?   # Precision
[hlL]?                          # Unused length modifier
(?P<format>[diouxXeEfFgGcrsa%]) # Conversion type

""", re.VERBOSE)