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.

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.

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?

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.

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

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.