paul j3 added the comment:
Glenn
I looked at your t18a.py test case
parser = ArgumentParser()
parser.add_argument('--foo', dest='foo')
parser.add_argument('--bar', dest='bar')
parser.add_argument('foz')
parser.add_argument('baz', nargs='*')
and parse variations on 'a b c d --foo x --bar 1'
I think your main problem is with the 'baz', nargs='*'. If nargs was changed
to '+', 'a --foo x b c d --bar 1' would work, returning {foz='a',
bar=['b','c','d']}.
argparse alternates between consuming positional and optionals until it runs
out of arguments or argument strings. But with '*', both 'foz' and 'baz' are
consumed with the first set of positional strings {foz='a', baz=[]}. When it
gets to 'b c d' there are no more positional arguments to consume, so they get
put into 'extras'.
With nargs='+', 'a b --foo x c d --bar 1' would assign {foz='a', baz=[b]}, and
extras=['c','d'].
So while optionals can be interspersed with positionals, they can't be placed
within the set of strings intended for one positional. That seems to me to very
reasonable (why break up 'b c d'?). And as your file demonstrates, you can
fall back on parse_known_args to handle the extras.
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nosy: +paul.j3
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue14191>
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