Python argparse：很多选择都会导致难看的帮助输出

Question

我有这个代码，我通常很满意：

import argparse

servers = [ "ApaServer", "BananServer", "GulServer", "SolServer", "RymdServer",
            "SkeppServer", "HavsServer", "PiratServer", "SvartServer", "NattServer", "SovServer" ]

parser = argparse.ArgumentParser(description="A program to update components on servers.")
group = parser.add_mutually_exclusive_group()
group.add_argument('-l', '--list', dest="update", action='store_false', default=False, help='list server components')
group.add_argument('-u', '--updatepom', dest="update", action='store_true', help='update server components')
parser.add_argument('-o', '--only', nargs='*', choices=servers, help='Space separated list of case sensitive server names to process')
parser.add_argument('-s', '--skip', nargs='*', choices=servers, help='Space separated list of case sensitive server names to exclude from processing')
args = parser.parse_args()

我喜欢choice=servers为我验证输入中的服务器名，这样就不必了。然而，有这么多有效的选择使得帮助输出看起来很糟糕：

usage: args.py [-h] [-l | -u]
               [-o [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} ...]]]
               [-s [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} ...]]]

A program to update components on servers.

optional arguments:
  -h, --help            show this help message and exit
  -l, --list            list server components
  -u, --updatepom       update server components
  -o [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} ...]], --only [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} ...]]
                        Space separated list of case sensitive server names to
                        process
  -s [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} ...]], --skip [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} [{ApaServer,BananServer,GulServer,SolServer,RymdServer,SkeppServer,HavsServer,PiratServer,SvartServer,NattServer,SovServer} ...]]
                        Space separated list of case sensitive server names to
                        exclude from processing

如果我想要，你会推荐哪种方式：

• 很好（主要是）自动生成的帮助输出
• 验证给定给-o或-s选项的条目是否在servers中。

奖金：

• 是否可以将不区分大小写的字符串与服务器名称匹配？

追加

我尝试使用michaelfilms建议，其中-o-s选项从上面的输出中删除，并添加此部分：

server optional arguments:
  Valid server names are: ApaServer, BananServer, GulServer, SolServer,
  RymdServer, SkeppServer, HavsServer, PiratServer, SvartServer,
  NattServer, SovServer

我认为它看起来不错，但是我真的需要为-o和-s选项提供帮助，否则用户不会知道它们。所以我还没有完全使用这种方法。

Answer 1

我有同样的问题，作为解决方法，我使用了epilog来描述每个选项的选择。我不得不使用argparse.RawTextHelpFormatter，它允许您指定epilog是预格式化的。

def choicesDescriptions():
   return """
Choices supports the following: 
   choice1         - the FIRST option
   choice2         - the SECOND option
   ...
   choiceN         - the Nth option
"""

def getChoices():
   return ["choice1", "choice2", ..., "choiceN"]

parser = argparse.ArgumentParser(formatter_class=argparse.RawTextHelpFormatter, epilog=choicesDescriptions())
parser.add_argument(
   'choices', 
   choices=getChoices(),
   help='Arg choice.  See the choices options below'
   )

args = parser.parse_args()
print(args)

Answer 2

我基本上重复了欧内斯特的话——为了避免一长串难看的选择，为基于选择的参数设置metavar='（尽管它不会去掉参数和逗号之间的空白（例如-o ,，而不是-o,）。然后，您可以在“常规描述”中详细描述可用的选项（如果您希望以明显缩进列出这些选项，RawDescriptionHelpFormatter在这里很有用）。

我不明白为什么欧内斯特的答案被否决了。此代码

import argparse

servers = [ "ApaServer", "BananServer", "GulServer", "SolServer", "RymdServer",
            "SkeppServer", "HavsServer", "PiratServer", "SvartServer", "NattServer", "SovServer" ]

parser = argparse.ArgumentParser(description="A program to update components on servers.")
group = parser.add_mutually_exclusive_group()
group.add_argument('-l', '--list', dest="update", action='store_false', default=False, help='list server components')
group.add_argument('-u', '--updatepom', dest="update", action='store_true', help='update server components')
parser.add_argument('-o', '--only', choices=servers, help='Space separated list of case sensitive server names to process.  Allowed values are '+', '.join(servers), metavar='')
parser.add_argument('-s', '--skip', choices=servers, help='Space separated list of case sensitive server names to exclude from processing.  Allowed values are '+', '.join(servers), metavar='')
args = parser.parse_args()

生成以下帮助输出

usage: run.py [-h] [-l | -u] [-o] [-s]

A program to update components on servers.

optional arguments:
  -h, --help       show this help message and exit
  -l, --list       list server components
  -u, --updatepom  update server components
  -o , --only      Space separated list of case sensitive server names to
                   process. Allowed values are ApaServer, BananServer,
                   GulServer, SolServer, RymdServer, SkeppServer, HavsServer,
                   PiratServer, SvartServer, NattServer, SovServer
  -s , --skip      Space separated list of case sensitive server names to
                   exclude from processing. Allowed values are ApaServer,
                   BananServer, GulServer, SolServer, RymdServer, SkeppServer,
                   HavsServer, PiratServer, SvartServer, NattServer, SovServer

希望这正是最初的帖子所寻找的。

Answer 3

不需要对任何东西进行子类化。只需使用要显示在帮助消息中的字符串传递一个metavar参数。

有关详细信息，请参见argparse documentation。