add argparse formatting option to display type names for metavar

[bethard]

BPO	11174
Files	11174.patch MetavarTypeHelpFormatter.diff

^{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 = None
closed_at = <Date 2011-03-26.13:52:54.925>
created_at = <Date 2011-02-10.15:45:51.456>
labels = ['type-feature', 'library']
title = 'add argparse formatting option to display type names for metavar'
updated_at = <Date 2015-10-19.21:33:22.677>
user = 'https://bugs.python.org/bethard'

bugs.python.org fields:

activity = <Date 2015-10-19.21:33:22.677>
actor = 'paul.j3'
assignee = 'bethard'
closed = True
closed_date = <Date 2011-03-26.13:52:54.925>
closer = 'bethard'
components = ['Library (Lib)']
creation = <Date 2011-02-10.15:45:51.456>
creator = 'bethard'
dependencies = []
files = ['20919', '21407']
hgrepos = []
issue_num = 11174
keywords = ['patch']
message_count = 6.0
messages = ['128300', '129577', '132230', '132231', '132237', '253197']
nosy_count = 4.0
nosy_names = ['bethard', 'gruszczy', 'python-dev', 'paul.j3']
pr_nums = []
priority = 'low'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue11174'
versions = ['Python 3.3']

[bethard]

Suggestion from a personal email:

I generally like my command line arguments that take a
value to specify the type, e.g.,

--runs int how many runs to do

Naturally I can do this using the metavars argument in every
add_argument() call, but that can become tedious. So I suggest adding a
metavars argument to the ArgumentParser constructor; default
metavars=None (current behaviour); metavars=type (show type names). And
of course, allow metavars specified in add_argument() calls to override
on a case by case basis.

[gruszczy]

First draft of patch with this functionality. Test, patch and docs are included. I'll gladly work further on this, so I would appreciate some advice and suggestions.

[bethard]

Sorry about such a slow response on this. Thanks for the patch!

I think rather than adding an ArgumentParser constructor parameter though, we should add a new formatter class. The attached patch allows you to write:

   >>> parser = argparse.ArgumentParser(
   ...     prog='PROG',
   ...     formatter_class=argparse.MetavarTypeHelpFormatter)
   >>> parser.add_argument('--foo', type=int)
   >>> parser.add_argument('bar', type=float)
   >>> parser.print_help()
   usage: PROG [-h] [--foo int] float

positional arguments:
float

optional arguments:
-h, --help show this help message and exit
--foo int

What do you think?

[gruszczy]

Well, since you are the designer of the package, I believe you have better knowledge on how to extend it :-). I just provided a patch according to what you described in the first message. Anyway having separate help formatter seems better than bloating parser's constructor.

[python-dev]

New changeset a15d65d8f269 by Steven Bethard in branch 'default':
Issue bpo-11174: Add argparse.MetavarTypeHelpFormatter, which uses type names
http://hg.python.org/cpython/rev/a15d65d8f269

[paulj3]

This formatter produces an error if one or more of the arguments uses the default None type (a string). This is because None does not have a .__name__.

This HelpFormatter probably has been rarely, if ever, used. The metavar parameter works just as well.