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copied!<p>You could use <a href="http://docs.python.org/dev/library/argparse.html#action" rel="nofollow">custom actions</a> for this:</p> <pre><code>import argparse import sys class VerifyNoBuild(argparse.Action): def __call__(self, parser, args, values, option_string=None): # print 'No: {n} {v} {o}'.format(n=args, v=values, o=option_string) if args.build is not None: parser.error( '--build should not be used with --from or --interval') setattr(args, self.dest, values) class VerifyOnlyBuild(argparse.Action): def __call__(self, parser, args, values, option_string=None): # print 'Only: {n} {v} {o}'.format(n=args, v=values, o=option_string) if getattr(args, 'from') is not None: parser.error('--from should not be used with --build') if getattr(args, 'interval') is not None: parser.error('--interval should not be used with --build') setattr(args, self.dest, values) parser = argparse.ArgumentParser(description='A Tool') subparsers = parser.add_subparsers(help='sub-command help') # create the parser for the 'download' command download_parser = subparsers.add_parser('download', help='download help') download_parser.add_argument('--interval', type=int, help='interval help', action=VerifyNoBuild) download_parser.add_argument('--from', type=int, action=VerifyNoBuild) download_parser.add_argument('--build', type=int, action=VerifyOnlyBuild) args = parser.parse_args('download --from 1234 --interval 60'.split()) print(args) # Namespace(build=None, from=1234, interval=60) args = parser.parse_args('download --build 1432'.split()) print(args) # Namespace(build=1432, from=None, interval=None) args = parser.parse_args('download --build 1432 --from 1234'.split()) print(args) # usage: test.py download [-h] [--interval INTERVAL] [--from FROM] [--build BUILD] # test.py download: error: --build should not be used with --from or --interval args = parser.parse_args('download --build 1432 --interval 60'.split()) print(args) # usage: test.py download [-h] [--interval INTERVAL] [--from FROM] [--build BUILD] # test.py download: error: --build should not be used with --from or --interval </code></pre> <p>But really, I think this is shorter and simpler:</p> <pre><code>def parse_options(): parser = argparse.ArgumentParser(description='A Tool') subparsers = parser.add_subparsers(help='sub-command help') #create the parser for the 'download' command download_parser = subparsers.add_parser('download', help='download help') download_parser.add_argument('--interval', type=int, help='interval help') download_parser.add_argument('--from', type=int) download_parser.add_argument('--build', type=int) opt=parser.parse_args() from_interval=[getattr(opt,key) is not None for key in ('from','interval')] if opt.build is not None: if any(from_interval): sys.exit('error!') elif not all(from_interval): sys.exit('error!') return opt </code></pre>

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