Arguments that are dependent on other arguments with Argparse

After you call parse_args on the ArgumentParser instance you've created, it'll give you a Namespace object. Simply check that if one of the arguments is present then the other one has to be there too. Like:

args = parser.parse_args()
if ('LoadFiles' in vars(args) and 
    'SourceFolder' not in vars(args) and 
    'SourceFile' not in vars(args)):

    parser.error('The -LoadFiles argument requires the -SourceFolder or -SourceFile')

You can use subparsers in argparse

 import argparse
 parser = argparse.ArgumentParser(prog='PROG')
 parser.add_argument('--foo', required=True, help='foo help')
 subparsers = parser.add_subparsers(help='sub-command help')

 # create the parser for the "bar" command
 parser_a = subparsers.add_parser('bar', help='a help')
 parser_a.add_argument('bar', type=int, help='bar help')
 print(parser.parse_args())

There are some argparse alternatives which you can easily manage cases like what you mentioned. packages like: click or docopt.

If we want to get around the manual implementation of chain arguments in argparse, check out the Commands and Groups in click for instance.