On 01/09/2015 03:44 PM, Adam Funk wrote:
I noticed in use that if an option with the 'append' action isn't
used, argparse assigns None to it rather than an empty list, &
confirmed this interactively:
#v+
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--foo', action='append')
_AppendAction(option_strings=['--foo'], dest='foo', nargs=None, const=None,
default=None, type=None, choices=None, help=None, metavar=None)
parser.add_argument('--bar', action='append')
_AppendAction(option_strings=['--bar'], dest='bar', nargs=None, const=None,
default=None, type=None, choices=None, help=None, metavar=None)
parser.parse_args('--foo 1 --foo 2'.split())
Namespace(bar=None, foo=['1', '2'])
#v-
Isn't that the exact behaviour documented here:
https://docs.python.org/3/library/argparse.html#default
where it says that the default for the default argument is None ?
I think Skip is right: you should be able to just add
default = []
to your arguments in the add_argument call.
Wolfgang
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