Looking For Best Way Of Giving Command Line Arguments In Python, Where Some Params Are Req For Some Option And Some Params Are Req For Other Options

Hi i am trying to send command line arguments for first time. The condition is that one parameter is required for one option and for others other parameter.(looking for user friend

Solution 1:

This variation on your script runs, and cleans up several things. It uses choices to control the options values. It omits unnecessary parameters in the other add_argument calls. It simplifies the post parse_args logic. help isn't really needed since there is always the -h option, but I included it as a choice. It falls through to the end because it is not in the action dictionary.

import argparse
import sys
class Stub(object):
    def __init__(self,s):
        self.s = s
    def __call__(self,conf_file, jobid):
        print self.s, conf_file, jobid
parser = argparse.ArgumentParser(description='Usage options.')
parser.add_argument('-o','--options', choices=('run','rerun','kill', 'resume', 'suspend','help'),required=True)
parser.add_argument('-c', '--config',help='config file input')
# optionals normally not required; 'file' not valid type
# argparse.FileType will open the file
parser.add_argument('-j', '--jobid',help='id of the job')
# str is the default type
args = parser.parse_args()
# action_arg = [args.options]
action = {'run': Stub('start_run'),
          'rerun': Stub('start_rerun'),
          'kill': Stub('kill_job'),
          'resume': Stub('resume_job'),
          'suspend': Stub('suspend_job'),
          #'get_run': get_run, # not in choices
          #'get_component': get_component,
          #'help': print_help,
          }.get(args.options)  # what's with the '-'.join?

if action:
    if args.options == "run":
        if args.config is None: # proper test for None
            print "Job configuration is needed to start a run and job id is not needed"
            sys.exit(2)
    elif args.options == "rerun":
        if args.config is None or args.jobid is None:
            print "Job configuration and jobid is needed to start a rerun."
            sys.exit(2)
    else:
        if args.jobid is None:
            print "Jobid is needed to perform %s action on job and configuration is not needed." %args.options
            sys.exit(2)
    action(args.config, args.jobid)
else:
    print "Usage Error:"
    parser.print_help()

This version replaces the options choices with subparsers. config and jobid become required arguments for the appropriate subparsers. I use parents to conveniently define the required mix and match. Now argparse does all the checking.

import argparse
class Stub(object):
    def __init__(self,s):
        self.s = s
    def __call__(self,conf_file, jobid):
        print self.s, conf_file, jobid

conf_parent = argparse.ArgumentParser(add_help=False)
conf_parent.add_argument('-c', '--config',help='config file input',required=True)
job_parent = argparse.ArgumentParser(add_help=False)
job_parent.add_argument('-j', '--jobid',help='id of the job',required=True)

parser = argparse.ArgumentParser(description='Usage options.')
parser.set_defaults(config=None, jobid=None) # put default value in namespace
sp = parser.add_subparsers(dest='options')
sp.add_parser('run',parents=[conf_parent])
sp.add_parser('rerun',parents=[conf_parent, job_parent])
sp.add_parser('kill',parents=[job_parent])
sp.add_parser('resume',parents=[job_parent])
sp.add_parser('suspend',parents=[job_parent])
args = parser.parse_args()

action = {'run': Stub('start_run'),
          'rerun': Stub('start_rerun'),
          'kill': Stub('kill_job'),
          'resume': Stub('resume_job'),
          'suspend': Stub('suspend_job'),
          }.get(args.options)
action(args.config, args.jobid)