Python argparse: combine multiple-value argument with default and const -

i've been looking solution add argument behave action='store_const', take multiple values.

so if don't pass @ all, should has no value(or value), if pass without value should has default value, , if pass value(s) should list of these values.

e.g.

parser.parse_args(''.split()) parser.parse_args('-a'.split()) parser.parse_args('-a 1 2 3'.split()) 

should result in

[none] [0] [1, 2, 3] 

not hard:

parser = argparse.argumentparser() parser.add_argument('-a',default=[none],action='store',type=int,nargs='*') print parser.parse_args(''.split()) print parser.parse_args('-a'.split()) print parser.parse_args('-a 1 2 3'.split()) 

if want special case -a no additional arguments, there no way without using custom action:

import argparse class myaction(argparse.action):     def __call__(self,parser,namespace,values,option_string=none):         if not values:             setattr(namespace,self.dest,[0])         else:             setattr(namespace,self.dest,values)  parser = argparse.argumentparser() parser.add_argument('-a',default=[none],action=myaction,type=int,nargs='*') print parser.parse_args(''.split()) print parser.parse_args('-a'.split()) print parser.parse_args('-a 1 2 3'.split())