python - Default argument alternative to None? -

i writing function little this:

def parse(string, default=none):     try:         ...  # body of function here     except parseerror:         if default not none:             return default         raise 

but run problems if want function return none.

if len(sys.argv) > 4:     if flag.ignore_invalid:         result = parse(sys.argv[4], none)  # still raises error     else:         result = parse(sys.argv[4]) 

what have tried fix is:

_default = object()  def parse(string, default=_default):     ...         if default not _default:             ... 

but seems i'm overthinking it, , seems there's easier way it.

the any , all functions (allowing none default), don't know how.

unless you're needing ignore parseerror, let parse throw of time, , catch in places need to:

try:     parse(sys.argv[4]) except parseerror:     if not flag.ignore_invalid:         raise 

though if must have default value, _default solution ok.