A typical example of Python's argparse combined with configparser . #python #argparse #configparser

argparse-example-1.py

import os
import logging
import argparse
import ConfigParser as configparser
from paste.deploy.converters import asbool, asint, aslist

#
# Declare expected command-line arguments
#

argp = argparse.ArgumentParser()

# Add positional arguments (many)
argp.add_argument ("inputs", metavar='INFILE', type=str, nargs='+',
    help='Provide input logs to parse and load into database');

# Add an optional string argument 'config' 
argp.add_argument ("-c", "--config", dest='config_file', default='config.ini', type=str);

# Add a optional switch (boolean optional argument)
argp.add_argument ("-v", "--verbose", dest='verbose', default=False, action='store_true',
    help='Be verbose');

# Parse command line    
args = argp.parse_args()

#
# Parse a config ini-style file
#

here = os.path.realpath('.')

config_file = args.config_file
logging.info('Reading configuration from %s' %(config_file))
config = configparser.ConfigParser(defaults = {'here': here})
config.read(args.config_file)

# Do something with them

if args.verbose:
    logging.info('Will produce verbose output')

sqla_url = config.get('main', 'sqlalchemy_url')

In this example the config file options will take precedence over command-line arguments, and in typical use cases the opposite is preferable.

Yes, but in the above example command-line arguments and config options are not conflicting

Isn't .setLevel(args.loggingLevel) better than having conditional if args.verbose's all around your code? For example;

argp.add_argument(
    '-l',
    '--log',
    help    = "Set logging level",
    choices = ['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'],
    nargs   = '?',
    dest    = "loggingLevel",
    const   = "INFO",
    default = DefaultConfiguration['DEFAULT']['LogLevel'],
    type    = str.upper
)

Then just handle convenience argument "-v" / "--verbose";

if args.verbose:
    args.loggingLevel = 'DEBUG'

Finally set the level;

syslog.setLevel(args.loggingLevel)

(or in .basicConfig().... which ever feels good)

Now you can just spam logging.debug(), logging.info() and so on and the logger takes care of it.

I will also chime in with MestreLion, this is not a typical use case. Like he said, the preferred order is to have a set of hardcoded configuration parameters in the code, which will first get overwritten by config.ini file and finally the command line arguments have the highest priority and they will overwrite whatever has been specified. You are missing the hardcoded configuration parameter data.