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argparse "usage" overly-complex with nargs="*" #82619

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bobjalex mannequin opened this issue Oct 10, 2019 · 11 comments
Closed

argparse "usage" overly-complex with nargs="*" #82619

bobjalex mannequin opened this issue Oct 10, 2019 · 11 comments
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@rhettinger
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3.9 only security fixes stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@bobjalex
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bobjalex mannequin commented Oct 10, 2019

BPO 38438
Nosy @rhettinger, @ericvsmith, @nicktimko, @brandtbucher, @CallumQuick
PRs
  • bpo-38438: Simplify argparse "star nargs" usage. #17106
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    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = 'https://github.com/rhettinger'
closed_at = <Date 2019-11-12.05:09:42.168>
created_at = <Date 2019-10-10.20:24:39.001>
labels = ['type-bug', 'library', '3.9']
title = 'argparse "usage" overly-complex with nargs="*"'
updated_at = <Date 2019-11-12.05:09:42.165>
user = 'https://bugs.python.org/bobjalex'

    bugs.python.org fields:

    activity = <Date 2019-11-12.05:09:42.165>
actor = 'rhettinger'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2019-11-12.05:09:42.168>
closer = 'rhettinger'
components = ['Library (Lib)']
creation = <Date 2019-10-10.20:24:39.001>
creator = 'bobjalex'
dependencies = []
files = []
hgrepos = []
issue_num = 38438
keywords = ['patch']
message_count = 11.0
messages = ['354402', '354410', '354419', '354450', '354457', '354467', '354475', '354476', '356354', '356386', '356411']
nosy_count = 7.0
nosy_names = ['rhettinger', 'eric.smith', 'paul.j3', 'bobjalex', 'nicktimko', 'brandtbucher', 'callumquick']
pr_nums = ['17106']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38438'
versions = ['Python 3.9']
    @bobjalex
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    bobjalex mannequin commented Oct 10, 2019

    This program:

    import argparse
ap = argparse.ArgumentParser()
ap.add_argument("arg", nargs="*")
ap.parse_args()

    Gives usage message:
    usage: help_complexity.py [-h] [arg [arg ...]]

    It's correct, but unnecessarily complex and challenging to the user.
    If I were manually writing the usage, arg... would do, or maybe [arg ...] to be consistent with other messages??

    @bobjalex bobjalex mannequin added 3.7 (EOL) end of life 3.8 only security fixes stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error labels Oct 10, 2019
    @ericvsmith
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    I think [arg ...] would make sense.

    Removing 3.5 and 3.6, since they're in security only mode. Adding 3.9.

    @ericvsmith ericvsmith added the 3.9 only security fixes label Oct 10, 2019
    @rhettinger
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    Bob, would like to create a PR?

    @rhettinger rhettinger self-assigned this Oct 11, 2019
    @brandtbucher
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    I’m happy to write one. This seems like a pretty straightforward fix.

    @rhettinger
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    Bob, as OP you get first dibs on a PR.
    Brandt, you're next in line :-)

    @nicktimko
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    nicktimko mannequin commented Oct 11, 2019

    The [arg [arg ...]] feels a bit more formal to me, and I might prefer it in the example shown where the arg name is fairly short. That said, man mv shows something like:

    mv [OPTION]... [-T] SOURCE DEST
mv [OPTION]... SOURCE... DIRECTORY
mv [OPTION]... -t DIRECTORY SOURCE...

    @brandtbucher
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    For backward compatibility with 2 metavars, the two-name form should still be possible. Just pass metavar=("FOO", "FOO").

    @ericvsmith
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    I don't think it's any more precise. It just seems verbose and confusing to me, while conveying the same information.

    [arg [arg ...]] to me means "optionally, an arg followed by one or more optional args".

    While [arg ...] to me means "optionally, one or more args".

    So, I'd vote for the simpler version, especially since we're presumably trying to communicate with people who aren't BNF or regex experts!

    @brandtbucher
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    I went ahead and opened a PR, since it's been a month.

    @rhettinger
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    New changeset a0ed99b by Raymond Hettinger (Brandt Bucher) in branch 'master':
    bpo-38438: Simplify argparse "star nargs" usage. (GH-17106)
    a0ed99b

    @rhettinger
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    Bob, thanks for the suggestion.

    Brandt, thanks for the PR.

    @rhettinger rhettinger removed 3.7 (EOL) end of life 3.8 only security fixes labels Nov 12, 2019
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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    @rhettinger rhettinger

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