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I would like to be able to change argparse default strings so the first word is capitalized. In lieu of that, I propose the attached patch to 2.7 which changes them in the source code.

Looks like "usage" is almost always lowercase in the programs I tried (ssh, svn, cat, etc.). So it probably wouldn't be a good idea to change the default. Seems like both this and issue 9694 need a better way to customize the text in argparse mesages.
As a temporary workaround for the group names, you can try:
parser._optionals.title = "Optional arguments"
parser._positionals.title = "Positional arguments"
I can't guarantee this will continue to work since it relies on internal details but at least it would work for the time being.

2.7 is closed to new features and I cannot see making a non-bug change in a maintenance release that could break something.
Should this be closed in favor of #9694? (Or vice versa?). Perhaps one of the issues should be renamed something like "Improve argparse message customization".

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> Should this be closed in favor of #9694? (Or vice versa?). Perhaps one of the issues should be renamed something like "Improve argparse message customization".
That sounds like a winner to me
-Tom

I'm moving this over to Issue 11695, which proposes support for a usage/help message template.
To customize the argument group names, the recommended approach is to create your own argument groups, and only put arguments there, e.g.:
parser = argparse.ArgumentParser(add_help=False)
flags = parser.add_argument_group('My Optional Arguments')
flags.add_argument('-h', '--help', action='help')
flags.add_argument('-v', action='version', version='1.3')
Then you'll get just the "My Optional Arguments" heading.