I have written the following sample code to demonstrate my issue.
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('-v', '--version', action='version',
version='%(prog)s 1.0')
parser.parse_args()
This produces the following help message.
$ python foo.py --help
usage: foo.py [-h] [-v]
optional arguments:
-h, --help show this help message and exit
-v, --version show program's version number and exit
I want to customize this help output such that it capitalizes all phrases and sentences, and puts period after sentences. In other words, I want the help message to be generated like this.
$ python foo.py --help
Usage: foo.py [-h] [-v]
Optional arguments:
-h, --help Show this help message and exit.
-v, --version Show program's version number and exit.
Is this something that I can control using the argparse API. If so, how? Could you please provide a small example that shows how this can be done?
First of all: capitalising those phrases flies in the face of convention, and argparse
isn't really tooled to help you change these strings easily. You have three different classes of strings here: boilerplate text from the help formatter, section titles, and help text per specific option. All these strings are localisable; you could just provide a 'capitalised' translation for all of these strings via the gettext()
module support. That said, you can reach in and replace all these strings if you are determined enough and read the source code a little.
The version
action includes a default help
text, but you can supply your own by setting the help
argument. The same applies to the help
action; if you set the add_help
argument to False
you can add that action manually:
parser = argparse.ArgumentParser(add_help=False)
parser.add_argument('-v', '--version', action='version',
version='%(prog)s 1.0', help="Show program's version number and exit.")
parser.add_argument('-h', '--help', action='help', default=argparse.SUPPRESS,
help='Show this help message and exit.')
Next, the optional arguments
message is a group title; each parser has two default groups, one for positional arguments, the other for optional. You can reach these by the attributes _positionals
and _optionals
, both of which have a title
attribute:
parser._positionals.title = 'Positional arguments'
parser._optionals.title = 'Optional arguments'
Be warned, by accessing names starting with an underscore you are venturing into the undocumented private API of the module, and your code may break in future updates.
Finally, to change the usage
string, you'll have to subclass the help formatter; pass the subclass in as the formatter_class
argument:
class CapitalisedHelpFormatter(argparse.HelpFormatter):
def add_usage(self, usage, actions, groups, prefix=None):
if prefix is None:
prefix = 'Usage: '
return super(CapitalisedHelpFormatter, self).add_usage(
usage, actions, groups, prefix)
parser = argparse.ArgumentParser(formatter_class=CapitalisedHelpFormatter)
Demo, putting these all together:
>>> import argparse
>>> class CapitalisedHelpFormatter(argparse.HelpFormatter):
... def add_usage(self, usage, actions, groups, prefix=None):
... if prefix is None:
... prefix = 'Usage: '
... return super(CapitalisedHelpFormatter, self).add_usage(
... usage, actions, groups, prefix)
...
>>> parser = argparse.ArgumentParser(add_help=False, formatter_class=CapitalisedHelpFormatter)
>>> parser._positionals.title = 'Positional arguments'
>>> parser._optionals.title = 'Optional arguments'
>>> parser.add_argument('-v', '--version', action='version',
... version='%(prog)s 1.0', help="Show program's version number and exit.")
_VersionAction(option_strings=['-v', '--version'], dest='version', nargs=0, const=None, default='==SUPPRESS==', type=None, choices=None, help="Show program's version number and exit.", metavar=None)
>>> parser.add_argument('-h', '--help', action='help', default=argparse.SUPPRESS,
... help='Show this help message and exit.')
_HelpAction(option_strings=['-h', '--help'], dest='help', nargs=0, const=None, default='==SUPPRESS==', type=None, choices=None, help='Show this help message and exit.', metavar=None)
>>> print(parser.format_help())
Usage: [-v] [-h]
Optional arguments:
-v, --version Show program's version number and exit.
-h, --help Show this help message and exit.