import abc
import argparse

# compatible with Python 2 *and* 3
ABC = abc.ABCMeta('ABC', (object,), {'__slots__': ()})

class Cmd(ABC): # export

    @abc.abstractmethod
    def run(self, args):
        pass

    def __init__(self, name, help):
        self.name = name
        self.help = help

    def _run(self, args):
        pass

    def add_parser(self, parsers):
        r = parsers.add_parser(self.name, help=self.help,
            formatter_class=argparse.ArgumentDefaultsHelpFormatter)
        r.set_defaults(func=self.run)
        return r