#!/usr/bin/env python

# Nick R. Papior, 2016, August

# This snippet shows that namespaces
# are not retained across subparsers.
#
# Example call:
#   $0 --foo first --bar
#   $0 first --bar
# Both of the above will fail due to the namespace.foo reference.
# This will work:
#   $0 first --foo --bar

from __future__ import print_function

import argparse as arg

# Create a parser and a subparser
p = arg.ArgumentParser()
# Add flag which is determining the top-level defaults
p.add_argument('--foo', action='store_true', default=False)

sp = p.add_subparsers()
sp1 = sp.add_parser('first')

# Add custom action
class BarAction(arg.Action):
    def __call__(self, parser, namespace, value, option_string=None):
        """ Try and access the `foo` variable """
        # Just to highlight the current namespace
        print(namespace.__dict__)
        # Perform action dependent on foo (this will error out as
        # the parent name-space is not passed... :()
        if namespace.foo:
            print('Do if TRUE')
        else:
            print('Do if FALSE')
            
sp1.add_argument('--bar', nargs=0, action=BarAction)
p.parse_args()