#! /usr/bin/env python
__doc__ = """
example of cascading options with ConfigParser and OptionParser
from : http://thoughtsbyclayg.blogspot.com/2009/10/python-over-riding-options-with.html
"""

# imports
import sys
from ConfigParser import ConfigParser
from optparse import OptionParser
# constants
default_option = 'default_value'
default_toggle = True

# classes
# internal functions

def main():
    # create a config parser
    # config parser objects store all options as strings
    config = ConfigParser({'option':str(default_option),
                           'toggle':str(default_toggle),
                          })
    config.read('example.cfg')

    # create command line option parser
    parser = OptionParser("%prog [options]" + __doc__.rstrip())

    # configure command line options
    parser.add_option("-o", "--option", action="store", dest="option", help="set option")
    parser.add_option("-t", "--toggleOff", action="store_false", dest="toggle", help="set toggle off")
    parser.add_option("-T", "--toggleOn", action="store_true", dest="toggle", help="set toggle on")

    # read config objects defaults section into a dictionary
    config_options = config.defaults()
    # config_options is dictionary of strings, over-ride toggle to bool
    for dest in [option.dest for option in parser.option_list if option.action.lower() in ('store_true', 'store_false')]:
        if config.has_option('DEFAULT', dest) and not isinstance(config_options[dest], bool):
            config_options[dest] = config.getboolean('DEFAULT',dest)

    # feed dictionary of defaults into parser object
    parser.set_defaults(**config_options)

    # parse command line options
    (options, args) = parser.parse_args()

    print parser.values

    return 0;

if __name__ == '__main__':
    status = main()
    sys.exit(status)