Python argparse with nargs behaviour incorrect

Question

Here is my argparse sample say sample.py

import argparse
parser = argparse.ArgumentParser()
parser.add_argument(\"-p\", nargs=\"+\", help=\"Stuff\")
args = p         


        

Answer 1

I ran into the same issue. I decided to go with the custom action route as suggested by mgilson.

import argparse
class ExtendAction(argparse.Action):
  def __call__(self, parser, namespace, values, option_string=None):
    if getattr(namespace, self.dest, None) is None:
      setattr(namespace, self.dest, [])
    getattr(namespace, self.dest).extend(values)
parser = argparse.ArgumentParser()
parser.add_argument("-p", nargs="+", help="Stuff", action=ExtendAction)
args = parser.parse_args()
print args

This results in

$ ./sample.py -p x -p y -p z w
Namespace(p=['x', 'y', 'z', 'w'])

Still, it would have been much neater if there was an action='extend' option in the library by default.