abs abs - 1 month ago 4
Python Question

Hiding selected subcommands using argparse

I am using argparse and have set-up subcommands to my program. I have created sub-parsers to define these sub-commands. I have some admin commands that shouldn't be shown to users in the help screen. I know we could hide arguments of a sub-command, but I don't know how we could hide few of the subcommands from showing up in the help list.

Here's my code snippet,

parser = argparse.ArgumentParser(prog='myProg',
description=desc,
formatter_class=argparse.RawDescriptionHelpFormatter)

subparsers = parser.add_subparsers(dest='sub_parser_name')


myProg_query.add_subparser(subparsers)
myProg_update.add_subparser(subparsers)
myProg_configure.add_subparser(subparsers)
myProg_result.add_subparser(subparsers)


When I run the help command, I get this

%> myProg --help
usage: myProg [-h]

positional arguments:
{query,update,configure,result}
query query information
update Update
configure Configure system
result tabulate the result


From the help output, I would want to display only "query" and "result" to the user. I tried to use argparse.SUPPRESS in add_subparser method, but it would hide all the subcommands. Whatever I searched only talked about hiding individual arguments of each sub-command, but not about hiding sub-command. I might have to create a custom formatter method, but wanted to check if there were any other way to achieve this.

Answer

metavar might do the trick:

import argparse
parser = argparse.ArgumentParser()
sp = parser.add_subparsers(metavar='{cmd1,cmd2}')
sp1 = sp.add_parser('cmd1')
sp2 = sp.add_parser('cmd2')
sp3 = sp.add_parser('cmd3')
parser.parse_args()

With this cmd3 does not appear in the usage or help. But it does appear in the error message

error: argument {cmd1,cmd2}: invalid choice: 'cmd' (choose from 'cmd1', 'cmd2', 'cmd3')


You may have already discovered this use of help=SUPPRESS. But it requires a custom usage (and possibly description) parameters:

import argparse
parser = argparse.ArgumentParser(usage='%(prog)s [-h] {cmd1,cmd2}')
sp = parser.add_subparsers(help=argparse.SUPPRESS)
sp1 = sp.add_parser('cmd1')
sp2 = sp.add_parser('cmd2')
sp3 = sp.add_parser('cmd3')
parser.parse_args()

To the main parser, subparsers look like choices of a positional argument. As best I can tell there isn't a way of selectively suppressing choices.


With this level of question, examining the argparse.py code itself can be more help than the docs. In this case I looked at the code for class _SubParsersAction(Action). That's doubly true if you want to customize the formatter. The existing alternative formatters modify just one or two methods buried deep in the class.


This issue has been raised as a bug issue, http://bugs.python.org/issue22848.

There is a patch that would modify the choices display based on help=SUPPRESS for individual subparsers. But I'm recommending the metavar solution, at least for now. There are other proposed patches for dealing with choices.

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