Stub that I find useful for writing CLI utilities

cli_stub.py

#!/usr/bin/env python2


"""

Given two tags, do absolutely nothing.

This script is just a stub illustrating the bits I re-use for every
CLI utility I write.

You should always post what you want it
to do up here, so you can remind yourself later what it was you were
working on.

"""


import sys

from optparse import OptionParser
from socket import gaierror
from xmlrpclib import Fault, ServerProxy


KOJI_SERVICE="http://redacted/"


def _debug_on(msg):
    print >> sys.stderr, msg
    
def _debug_off(msg):
    pass


def _verbose_on(msg):
    print msg

def _verbose_off(msg):
    pass



class ForgotMyWork(Exception):
    pass


def do_work():
    raise ForgotMyWork("I forgot to make this script do anything")


# Do the important stuff here.
def cli(options, release_tag, candidate_tag):
        
    kojihub = ServerProxy(options.koji)

    debug = _debug_on if options.debug else _debug_off
    verbose = _verbose_on if options.verbose else _verbose_off

    debug("starting to work on secret stuff")
    verbose("Did Zero Work!")
    
    do_work()


def create_optparser():
    parse = OptionParser("%prog [OPTIONS] TAG_A TAG_B",
                         description="Do something with two tags")

    parse.add_option("--reverse", action="store_true", default=False,
                     help="reverse behavior")

    parse.add_option("--inherit", action="store_true", default=False,
                     help="look through the entire inheritance")

    parse.add_option("--koji", action="store", default=KOJI_SERVICE,
                     help="URI for the koji XMLRPC service")

    parse.add_option("--debug", action="store_true",
                     help="print debugging output")

    parse.add_option("--verbose", action="store_true",
                     help="print verbose messages")

    return parse


def main(args):
    parser = create_optparser()
    options, args = parser.parse_args(args)
    
    if len(args) > 3:
        parser.error("Too many arguments!")

    elif len(args) < 3:
        parser.error("Not enough arguments!")

    # this is a good place to check any argument and options for
    # sanity, so you can barf out the parser help message.

    # unpack the real arguments that you want here
    name, release, candidate = args

    try:
        # if there are "expected" exceptions, such as NoSuchFile,
        # NoSuchTag, make up your own exception classes and raise them
        # from the cli function, and catch them here, then return the
        # appropriate code if any.
        cli(options, release, candidate)
        
    except KeyboardInterrupt, ki:
        return 130
        
    except Fault, xmlf:
        print >> sys.stderr, xmlf.faultString
        return -1

    except gaierror, dns:
        print >> sys.stderr, dns.message
        print >> sys.stderr, "Try using --koji with an IP address"
        return -2

    except ForgotMyWork, fml:
        print >> sys.stderr, fml

    else:
        return 0


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


#
# The end.

Some things worth considering; if there is a lot of output, it could be worth setting the debug and verbose functions to be at the top level.