On 3/15/11 12:46 PM, 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.
I think that would work fine for most cases. Just be careful with the argument
types that may consume resources. E.g. type=argparse.FileType().
You could also make a secondary parser that just extracts the config-file
argument:
[~]
|25> import argparse
[~]
|26> config_parser = argparse.ArgumentParser(add_help=False)
[~]
|27> config_parser.add_argument('-c', '--config', action='append')
_AppendAction(option_strings=['-c', '--config'], dest='config', nargs=None,
const=None, default=None, type=None, choices=None, help=None, metavar=None)
[~]
|28> parser = argparse.ArgumentParser()
[~]
|29> parser.add_argument('-c', '--config', action='append') # For the --help
string.
_AppendAction(option_strings=['-c', '--config'], dest='config', nargs=None,
const=None, default=None, type=None, choices=None, help=None, metavar=None)
[~]
|30> parser.add_argument('-o', '--output')
_StoreAction(option_strings=['-o', '--output'], dest='output', nargs=None,
const=None, default=None, type=None, choices=None, help=None, metavar=None)
[~]
|31> parser.add_argument('other', nargs='*')
_StoreAction(option_strings=[], dest='other', nargs='*', const=None,
default=None, type=None, choices=None, help=None, metavar=None)
[~]
|32> argv = ['-c', 'config-file.json', '-o', 'output.txt', 'other', 'arguments']
[~]
|33> known, unknown = config_parser.parse_known_args(argv)
[~]
|34> known
Namespace(config=['config-file.json'])
[~]
|35> unknown
['-o', 'output.txt', 'other', 'arguments']
[~]
|36> for cf in known.config:
...> # Load d from file.
...> parser.set_defaults(**d)
...>
[~]
|37> parser.parse_args(unknown)
Namespace(config=None, other=['other', 'arguments'], output='output.txt')
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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