如何使python argparse不带前缀的互斥组参数？

Python2.7 argparse只接受互斥组中的可选参数（前缀）：

parser = argparse.ArgumentParser(prog='mydaemon') action = parser.add_mutually_exclusive_group(required=True) action.add_argument('--start', action='store_true', help='Starts %(prog)s daemon') action.add_argument('--stop', action='store_true', help='Stops %(prog)s daemon') action.add_argument('--restart', action='store_true', help='Restarts %(prog)s daemon') 

$ mydaemon -h

 usage: mydaemon [-h] (--start | --stop | --restart) optional arguments: -h, --help show this help message and exit --start Starts mydaemon daemon --stop Stops mydaemon daemon --restart Restarts mydaemon daemon 

有没有办法使argparse参数的行为像传统的Unix守护进程控制：

 (start | stop | restart) and not (--start | --stop | --restart) ? 

Answer 1

对于argparse所有能力和选项，我不认为你会得到一个看起来像你想要的“canned”用法string。

那就是说，你从原来的post开始看了子parsing器吗？

这是一个准系统的实现：

 import argparse parser = argparse.ArgumentParser(prog='mydaemon') sp = parser.add_subparsers() sp_start = sp.add_parser('start', help='Starts %(prog)s daemon') sp_stop = sp.add_parser('stop', help='Stops %(prog)s daemon') sp_restart = sp.add_parser('restart', help='Restarts %(prog)s daemon') parser.parse_args() 

使用-h选项运行此操作会产生：

 usage: mydaemon [-h] {start,stop,restart} ... positional arguments: {start,stop,restart} start Starts mydaemon daemon stop Stops mydaemon daemon restart Restarts mydaemon daemon 

这种方法的好处之一是能够使用set_defaults为每个子分析器直接挂接一个函数的参数。 我还添加了一个“优雅”选项stop和restart ：

 import argparse def my_stop(args): if args.gracefully: print "Let's try to stop..." else: print 'Stop, now!' parser = argparse.ArgumentParser(prog='mydaemon') graceful = argparse.ArgumentParser(add_help=False) graceful.add_argument('-g', '--gracefully', action='store_true', help='tries to terminate the process gracefully') sp = parser.add_subparsers() sp_start = sp.add_parser('start', help='Starts %(prog)s daemon') sp_stop = sp.add_parser('stop', parents=[graceful], description='Stops the daemon if it is currently running.', help='Stops %(prog)s daemon') sp_restart = sp.add_parser('restart', parents=[graceful], help='Restarts %(prog)s daemon') sp_stop.set_defaults(func=my_stop) args = parser.parse_args() args.func(args) 

显示stop的“帮助”信息：

 $ python mydaemon.py stop -h usage: mydaemon stop [-h] [-g] Stops the daemon if it is currently running. optional arguments: -h, --help show this help message and exit -g, --gracefully tries to terminate the process gracefully 

停止“优雅”：

 $ python mydaemon.py stop -g Let's try to stop... 

Answer 2

这听起来像你想要一个位置的参数，而不是相互排斥的选项。 您可以使用“选项”来限制可能的可接受选项。

 parser = ArgumentParser() parser.add_argument('action', choices=('start', 'stop', 'restart')) 

这会产生如下的使用线：

 usage: foo.py [-h] {start,stop,restart} 

Answer 3

从pymotw

 import argparse parser = argparse.ArgumentParser() group = parser.add_mutually_exclusive_group() group.add_argument('-a', action='store_true') group.add_argument('-b', action='store_true') print parser.parse_args() 

输出：

 $ python argparse_mutually_exclusive.py -h usage: argparse_mutually_exclusive.py [-h] [-a | -b] optional arguments: -h, --help show this help message and exit -a -b $ python argparse_mutually_exclusive.py -a Namespace(a=True, b=False) $ python argparse_mutually_exclusive.py -b Namespace(a=False, b=True) $ python argparse_mutually_exclusive.py -a -b usage: argparse_mutually_exclusive.py [-h] [-a | -b] argparse_mutually_exclusive.py: error: argument -b: not allowed with argument -a 

版本2

 import argparse parser = argparse.ArgumentParser() subparsers = parser.add_subparsers(help='commands') # A list command list_parser = subparsers.add_parser('list', help='List contents') list_parser.add_argument('dirname', action='store', help='Directory to list') # A create command create_parser = subparsers.add_parser('create', help='Create a directory') create_parser.add_argument('dirname', action='store', help='New directory to create') create_parser.add_argument('--read-only', default=False, action='store_true', help='Set permissions to prevent writing to the directory', ) # A delete command delete_parser = subparsers.add_parser('delete', help='Remove a directory') delete_parser.add_argument('dirname', action='store', help='The directory to remove') delete_parser.add_argument('--recursive', '-r', default=False, action='store_true', help='Remove the contents of the directory, too', ) print parser.parse_args(['list', 'as d', ]) >>> Namespace(dirname='as d') print parser.parse_args(['list', 'as d', 'create' ]) >>> error: unrecognized arguments: create 

Answer 4

build立在亚当的答案…如果你想指定一个默认值，你总是可以做以下的事情，这样他们可以有效地把它留空。

 import argparse ActionHelp = """ Start = Starts the daemon (default) Stop = Stops the daemon Restart = Restarts the daemon """ parser = argparse.ArgumentParser(formatter_class=argparse.RawTextHelpFormatter) parser.add_argument('action', nargs = '?', choices=('start', 'stop', 'restart'), default = 'start', help = ActionHelp) print parser.parse_args(''.split()) print print parser.parse_args('-h'.split()) 

这将打印：

 Namespace(action='start') usage: program.py [-h] [{start,stop,restart}] postional arguments: {start,stop,restart} Start = Starts the daemon (default) Stop = Stops the daemon Restart = Restarts the daemon optional arguments: -h, --help show this help message and exit