Question

I’ve been using optparse for a while now, and would like to add the ability to load the arguments from a config file.

So far the best I can think of is a wrapper batch script with the arguments hardcoded… seems clunky.

What is the most elegant way to do this?

Answer 1

I agree with S.Lott’s idea of using a config file, but I’d recommend using the built-in ConfigParser (configparser in 3.0) module to parse it, rather than a home-brewed solution.

Here’s a brief script that illustrates ConfigParser and optparse in action.

import ConfigParser
from optparse import OptionParser

CONFIG_FILENAME = 'defaults.cfg'

def main():
    config = ConfigParser.ConfigParser()
    config.read(CONFIG_FILENAME)

    parser = OptionParser()
    parser.add_option("-l",
                      "--language",
                      dest="language",
                      help="The UI language",
                      default=config.get("Localization", "language"))
    parser.add_option("-f",
                      "--flag",
                      dest="flag",
                      help="The country flag",
                      default=config.get("Localization", "flag"))

    print parser.parse_args()

if __name__ == "__main__":
    main()

Output:

(<Values at 0x2182c88: {'flag': 'japan.png', 'language': 'Japanese'}>, [])

Run with “parser.py --language=French“:

(<Values at 0x2215c60: {'flag': 'japan.png', 'language': 'French'}>, [])

Help is built in.
Run with “parser.py --help“:

Usage: parser.py [options]

Options:
  -h, --help            show this help message and exit
  -l LANGUAGE, --language=LANGUAGE
                        The UI language
  -f FLAG, --flag=FLAG  The country flag

The config file:

[Localization]
language=Japanese
flag=japan.png