argparse, tell if arg was defaulted

[Jean-Michel Pichavant]

Neal Becker wrote:
> Robert Kern wrote:
>
>   
>> On 3/15/11 9:54 AM, Neal Becker wrote:
>>     
>>> Is there any way to tell if an arg value was defaulted vs. set on command
>>> line?
>>>       
>> No. If you need to determine that, don't set a default value in the
>> add_argument() method. Then just check for None and replace it with the
>> default value and do whatever other processing for the case where the user
>> does not specify that argument.
>>
>> parser.add_argument('-f', '--foo', help="the foo argument [default: bar]")
>>
>> args = parser.parse_args()
>> if args.foo is None:
>>      args.foo = 'bar'
>>      print 'I'm warning you that you did not specify a --foo argument.'
>>      print 'Using default=bar.'
>>
>>     
>
> Not a completely silly use case, actually.  What I need here is a combined 
> command line / config file parser.
>
> Here is my current idea:
> -----------------------------
>
> parser = OptionParser()
> parser.add_option ('--opt1', default=default1)
>
> (opt,args) = parser.parse_args()
>
> import json, sys
>
> for arg in args:
>     print 'arg:', arg
>     d = json.load(open (arg, 'r'))
>     parser.set_defaults (**d)
>
> (opt,args) = parser.parse_args()
> -----------------------
>
> parse_args() is called 2 times.  First time is just to find the non-option args, 
> which are assumed to be the name(s) of config file(s) to read.  This is used to 
> set_defaults.  Then run parse_args() again.
>
>   
Is that what you want ?

"user CLI > json defaults > script default"

If so, your idea seems good.

Otherwise
"--opt1" in sys.argv

would tell you if an option has been specified through the CLI. But it 
seems to me anti-pattern. You should not need to parse the CLI, that's 
the purpose of using optparse.

JM