Issue 25307: Enhancing the argparse help output (original) (raw)

I'm noticing some things on the argparse help output that can maybe enhanced. Here is a testcase that produces an example output:

#!/usr/bin/python3 -BEOObbs

coding=utf-8

import argparse arguments = argparse.ArgumentParser() arguments.add_argument('-t', '--test1', action = 'store_true', help = 'Description1') arguments.add_argument('--test2', action = 'store_true', help = 'Description2') arguments.add_argument('-u', '--test3', choices = ['choice1', 'choice2'], help = 'Description3', nargs = '+') arguments.parse_args()

• A way to automatically indent names or to give the user a way to control the indentation would make them easier to read. For example --test2 is here under a short option but it would be easier to read if it would have an offset to be directly under --test1.
• The line "-u {choice1,choice2} [{choice1,choice2} ...], --test3 {choice1,choice2} [{choice1,choice2} ...]" shows the choices for every name while they are the same. Maybe they can be shortened to be shown only on the last name like "-u, --test3 {choice1,choice2} [{choice1,choice2} ...]".

Formatter _format_action_invocation(self, action) is the key function. Notice how it treats positionals and optionals separately. Also it calls

default = self._get_default_metavar_for_optional(action)
args_string = self._format_args(action, default)

to get the string that is placed after each option_string.

'choices' are incorporated via the _metavar_formatter() method (through several function calls). They do not get their own separate consideration. Tracing this calling stack is not a trivial task.

But if you want custom behavior at this point in the help, _format_action_invocation() is the function to play with. You could even add the space for a nonexistent short option at this point.

http://bugs.python.org/issue16468 is an example of a 'choices' thread. Note that a formatted list of choices is also shown in the 'usage' and error messages. It's about formatting the choices string, not about where to show it.