python - How to figure out which command line parameters have been set in plac? -

my python script takes configuration values in order:

1. command line argument (possibility overwrite user defined values in configuration file)
2. configuration file value (user defined values)
3. default value in source code

i need figure out option has been set on command line in order determine whether default value has been set explicitly or not. plac [not?] transparent , don't see how it's possible. avoid parse sys.argv because writing command line parser in order use command line parser doesn't seem idea.

i'm using plac 0.9.1 on ubuntu 15.04.

could give simple example of plac setup? used know well, know underlying argparse better.

are using plac invoke function(s) directly, e.g.

plac.call(main) 

internally plac creates argparse.argumentparser (actually own subclass), populates arguments derived functions signature. , calls function values parsed.

if working argparse directly, create parser, populate it, , invoke with

args = parser.parse_args() 

args namespace object attributes named after arguments. can converted dictionary.

if go argparse route (possibly still creating parser plac), can check attributes in args, , compare values defaults, or config file values.

ipython populates argparse.parser arguments derived config files (default , custom). lets on ride config defaults @ several stages - custom files or commandline.

plac supposed easier argparse, integrating parser creation , function calling. in case may better separate steps.

---

the code plac.call is:

def call(obj, arglist=sys.argv[1:], eager=true):    ...    cmd, result = parser_from(obj).consume(arglist)    ... 

the first part creates parser; arguments of parser based on annotations decorator. main in test plac documentation.

in [22]: p=plac.parser_from(main)  in [23]: p out[23]: argumentparser(prog='ipython2.7', usage=none, description=none, version=none, formatter_class=<class 'argparse.rawdescriptionhelpformatter'>, conflict_handler='error', add_help=true) 

p.consume longer function, checks things subparsers. @ point does

ns, extraopts = self.parse_known_args(arglist)    # or self.parse_args 

ns argparse namespace, parameters set parser - both defaults , ones command line. calls 'the function' values ns (split python positional args , keyword args).

so can call parser directly:

in [25]: p.parse_args([])    # or default sys.argv[1:] out[25]: namespace(args=[], kw={}, opt=none) 

the p.print_help() shows arguments expects commandline, in neatly formatted form.

and if want further argparse guts can @ p._actions, list of argparse.action objects uses parse commandline.