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To add an optional argument, simply omit the required parameter in add_argument() . args = parser. parse_args()if args.
The argparse module provides a convenient interface to handle command-line arguments. It displays the generic usage of the program, help, and errors. The parse_args() function of the ArgumentParser class parses arguments and adds value as an attribute dest of the object.
The store_true option automatically creates a default value of False. Likewise, store_false will default to True when the command-line argument is not present.
def make_action(additional_arg):
class customAction(argparse.Action):
def __call__(self, parser, args, values, option_string=None):
print(additional_arg)
setattr(args, self.dest, values)
return customAction
#...
parser.add_argument('-e', '--example', action=make_action('your arg'))
Another solution is to derive the based class argparse.Action like this:
class CustomAction(argparse.Action):
def __init__(self,option_strings,
additional_arg1,additional_arg2,
dest=None,
nargs=0,
default=None,
required=False,
type=None,
metavar=None,
help=None):
self._a1=additional_arg1
self._a2=additional_arg2
super(CustomAction, self).__init__(
option_strings=option_strings,
dest=dest,
nargs=nargs,
default=default,
required=required,
metavar=metavar,
type=type,
help=help)
def __call__(self, parser, namespace, values, option_string=None):
print(self._a1)
print(self._a2)
setattr(args, self.dest, values)
#........
parser.add_argument('-e', '--example', action=CustomAction, additional_arg1='your arg', additional_arg2=42)
Alternatively, supply *args and **kwargs to pass through any additional parameters to the parent constructor.
class CustomAction(argparse.Action):
def __init__(self, option_strings, additional_arg1, additional_arg2,
*args, **kwargs):
self._a1 = additional_arg1
self._a2 = additional_arg2
super(CustomAction, self).__init__(option_strings=option_strings,
*args, **kwargs)
def __call__(self, parser, namespace, values, option_string=None):
print(self._a1)
print(self._a2)
setattr(args, self.dest, values)
#........
parser.add_argument('-e', '--example', action=CustomAction, additional_arg1='your arg', additional_arg2=42)
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