[issue20333] argparse subparser usage message hides main parser usage
paul j3 added the comment: When `add_subparsers` creates the `_prog_prefix` it uses a list of positionals. That makes sense, since a subparser argument is positional, so the user needs to know where it fits in the broader scope of positionals. But it intentionally skips the 'optionals'. The problem in the example for this bug is that its 'optional' is 'required'. A fix is to include all 'required optionals' along with positionals in the usage prefix. Attached is a partial patch that does this. I also question whether it makes sense to include 'mutually_exclusive_groups' in this usage formatting, since all actions in such a group must be non-required. And such a group can include at most one positional (with ? or *). A MXG is marked only if all of its actions are present in the usage list. The programmer can also customize the subparsers usage with the 'prog' keyword of either the 'add_subparsers' or 'add_parser' commands. I illustrate this in the attached 'sample.py' script. 'test_argparse.py' does not seem to test this issue much. Atleast it isn't bothered by these tweaks. Note that any arguments added to the main parser after the 'add_subparsers' command will not appear the subparser usage, since this is defined when the subparsers are created. -- keywords: +patch Added file: http://bugs.python.org/file35203/issue20333.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue20333 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue20333] argparse subparser usage message hides main parser usage
Changes by paul j3 ajipa...@gmail.com: Added file: http://bugs.python.org/file35204/sample.py ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue20333 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue20333] argparse subparser usage message hides main parser usage
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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[issue20333] argparse subparser usage message hides main parser usage
Changes by Berker Peksag berker.pek...@gmail.com: -- nosy: +bethard, paul.j3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue20333 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
