Parsing the command line

Code from http://krondo.com/?p=1247

import optparse

def parse_args():
    usage = """usage: %prog [options] poetry-file
    This is the Slow Poetry Server, blocking edition.
    Run it like this
    python slowpoetry.py 

    If you are in the base directory of the twisted-intro package,
    you could run it like this:
    python blocking-server/slowpoetry.py poetry/ecstasy.txt

    to serve up John Donne's Ecstasy, which I know you want to do.
    """

    parser = optparse.OptionParser(usage)

    help = "The port to listen on. Default to a random available port."
    parser.add_option('--port', type='int', help=help)

    help = "The interface to listen on. Default is localhost."
    parser.add_option('--iface', help=help, default='localhost')

    help = "The number of seconds between sending bytes."
    parser.add_option('--delay', type='float', help=help, default=.1)

    help = "The number of bytes to send at a time."
    parser.add_option('--num-bytes', type='int', help=help, default=10)

    options, args = parser.parse_args()

    if len(args) != 1:
    parser.error('Provide exactly one poetry file.')

    poetry_file = args[0]

    if not os.path.exists(args[0]):
    parser.error('No such file: %s' % poetry_file)

    return options, poetry_file

def main():
    options, poetry_file= parse_args()
    
    # options attributes can then be used like this :
    # options.num-bytes, options.delay, options.port and so on...