# coding: utf-8

import argparse


class CountAction(argparse.Action):
    """argparse action for counting up and down

    parser = argparse.ArgumentParser()
    parser.add_argument('--verbose', '-v', action=CountAction, const=1, nargs=0)
    parser.add_argument('--quiet', '-q', action=CountAction, dest='verbose',
            const=-1, nargs=0)
    """
    def __call__(self, parser, namespace, values, option_string=None):
        try:
            val = getattr(namespace, self.dest) + self.const
        except TypeError: # probably None
            val = self.const
        setattr(namespace, self.dest, val)