New submission from Martin d'Anjou:
Consider the following code:
#!/usr/bin/env python3
import argparse
# create the top-level parser
parser = argparse.ArgumentParser(prog='PROG')
parser.add_argument('--file', help='A filename', required=True)
subparsers = parser.add_subparsers(help='sub-command help')
# create the parser for the "a" command
parser_a = subparsers.add_parser('a', help='a help')
parser_a.add_argument('bar', type=int, help='bar help')
# create the parser for the "b" command
parser_b = subparsers.add_parser('b', help='b help')
parser_b.add_argument('--baz', choices='XYZ', help='baz help')
The help for subparser a is obtained with: parser.parse_args(["a","--help"])
usage: PROG a [-h] bar
positional arguments:
bar bar help
optional arguments:
-h, --help show this help message and exit
When the user follows the help, the user gets it wrong:
parser.parse_args(["a","10"])
usage: PROG [-h] --file FILE {a,b} ...
PROG: error: argument --file is required
The correct way to use the subparser is:
parser.parse_args(["--file","file","a","10"])
But the problem is that the original help message is not telling the user that
this is the correct way. When asking for the "a" subparser help, the usage
message should also reveal the main parser arguments. Continuing with the
example, something like this should be appropriate:
usage: PROG [-h] --file FILE a [-h] bar
This is how the argparse Java port works.
----------
components: Library (Lib)
messages: 208670
nosy: Martin.d'Anjou
priority: normal
severity: normal
status: open
title: argparse subparser usage message hides main parser usage
type: enhancement
versions: Python 3.3
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue20333>
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