Which is the best way to allow configuration options be overridden at the command line in Python?

Question

I have a Python application which needs quite a few (~30) configuration parameters. Up to now, I used the OptionParser class to define default values in the app itself, with

Answer 1

I can't say it's the best way, but I have an OptionParser class that I made that does just that - acts like optparse.OptionParser with defaults coming from a config file section. You can have it...

class OptionParser(optparse.OptionParser):
    def __init__(self, **kwargs):
        import sys
        import os
        config_file = kwargs.pop('config_file',
                                 os.path.splitext(os.path.basename(sys.argv[0]))[0] + '.config')
        self.config_section = kwargs.pop('config_section', 'OPTIONS')

        self.configParser = ConfigParser()
        self.configParser.read(config_file)

        optparse.OptionParser.__init__(self, **kwargs)

    def add_option(self, *args, **kwargs):
        option = optparse.OptionParser.add_option(self, *args, **kwargs)
        name = option.get_opt_string()
        if name.startswith('--'):
            name = name[2:]
            if self.configParser.has_option(self.config_section, name):
                self.set_default(name, self.configParser.get(self.config_section, name))

Feel free to browse the source. Tests are in a sibling directory.