如何使python argparse不带前缀的互斥组参数?

Python2.7 argparse only accepts optional arguments (prefixed) in mutually exclusive groups:

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

美元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

Is there a way to make argparse arguments behaves like traditional unix daemon control:

有没有一种方法可以使argparse参数像传统的unix守护进程控件那样运行:

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

4 个解决方案

#1

For all the abilities and options in argparse I don't think you'll ever get a "canned" usage string that looks like what you want.

对于argparse的所有功能和选项，我不认为您会得到一个“罐装”的使用字符串，它看起来像您想要的。

That said, have you looked at sub-parsers since your original post?

也就是说，从你最初的帖子开始，你看过子解析器了吗?

Here's a barebones implementation:

这是一个贫乏的实现:

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()

Running this with the -h option yields:

使用-h选项运行此操作可以得到:

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

positional arguments:
  {start,stop,restart}
    start               Starts mydaemon daemon
    stop                Stops mydaemon daemon
    restart             Restarts mydaemon daemon

One of the benefits of this approach is being able to use set_defaults for each sub-parser to hook up a function directly to the argument. I've also added a "graceful" option for stop and restart:

这种方法的好处之一是可以为每个子解析器使用set_defaults来将函数直接连接到参数。我还添加了一个“优雅”的停止和重新启动选项:

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')

# Hook subparsers up to functions
sp_stop.set_defaults(func=my_stop)

# Uncomment when my_start() and 
# my_restart() are implemented
#
# sp_start.set_defaults(func=my_start)
# sp_restart.set_defaults(func=my_restart)

args = parser.parse_args()
args.func(args)

Showing the "help" message for stop:

显示停止的“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

Stopping "gracefully":

停止“优雅”:

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

#2

It sounds like you want a positional argument instead of mutually exclusive options. You can use 'choices' to restrict the possible acceptable options.

听起来你想要一个位置参数而不是相互排斥的选项。您可以使用“选择”来限制可能的可接受选项。

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

This produces a usage line that looks like this:

这就产生了一个这样的用法:

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

#3

from pymotw

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()

output:

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

version2

version2

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', 'a s d', ])
>>> Namespace(dirname='a s d')
print parser.parse_args(['list', 'a s d', 'create' ])
>>> error: unrecognized arguments: create

#4

Building on Adam's answer... if you wanted to specify a default you could always do the following so they can effectively leave it blank.

建立在亚当的回答…如果您想指定一个默认值，您可以始终执行以下操作，以便它们可以有效地将其保留为空。

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())

which will print:

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