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nargs='+' doesn't work the way I expected:
>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument("--name", dest='names', nargs='+')
_StoreAction(option_strings=['--name'], dest='names', nargs='+', const=None, default=None, type=None, choices=None, help=None, metavar=None)
>>> parser.parse_args('--name foo --name bar'.split())
Namespace(names=['bar'])
I can "fix" this by using --name foo bar, but that's unlike other tools I've used, and I'd rather be more explicit. Does argparse support this?
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Optional Arguments To add an optional argument, simply omit the required parameter in add_argument() . args = parser. parse_args()if args.
Python argparse optional argument The example adds one argument having two options: a short -o and a long --ouput . These are optional arguments. The module is imported. An argument is added with add_argument .
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. dest identifies an argument.
You want to use action='append' instead of nargs='+':
>>> parser.add_argument("--name", dest='names', action='append')
_AppendAction(option_strings=['--name'], dest='names', nargs=None, const=None, default=None, type=None, choices=None, help=None, metavar=None)
>>> parser.parse_args('--name foo --name bar'.split())
Namespace(names=['foo', 'bar'])
nargs is used if you just want to take a series of positional arguments, while action='append' works if you want to be able to take a flag more than once and accumulate the results in a list.
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