argparse subparser monolithic help output

Question

My argparse has only 3 flags (store_true) on the top level, everything else is handled through subparsers. When I run `myprog.py --help`, the output shows a list of all subcommands like normal, `{sub1, sub2, sub3, sub4, ...}`. So, the default is working great... I usually can't remember the exact subcommand name I need, and all of its options. So I end up doing 2 help lookups: ``` myprog.py --help myprog.py sub1 --help ``` I do this so often, I decided to cram this into one step. I would rather have my toplevel help output a huge summary, and then I scroll through the list manually. I find it is much faster (for me at least). I was using a RawDescriptionHelpFormatter, and typing the long help output by hand. But now I have lots of subcommands, and its becoming a pain to manage. Is there a way to get a verbose help output with just one program call? If not, how can I iterate the subparsers of my argparse instance, and then retrieve the help output individually from each one (which I wi…

Accepted Answer

This is a bit tricky, as argparse does not expose a list of defined sub-parsers directly. But it can be done:

```
import argparse

# create the top-level parser
parser = argparse.ArgumentParser(prog='PROG')
parser.add_argument('--foo', action='store_true', help='foo help')
subparsers = parser.add_subparsers(help='sub-command help')

# create the parser for the "a" command
parser_a = subparsers.add_parser('a', help='a help')
parser_a.add_argument('bar', type=int, help='bar help')

# create the parser for the "b" command
parser_b = subparsers.add_parser('b', help='b help')
parser_b.add_argument('--baz', choices='XYZ', help='baz help')
# print main help
print(parser.format_help())

# retrieve subparsers from parser
subparsers_actions = [
    action for action in parser._actions 
    if isinstance(action, argparse._SubParsersAction)]
# there will probably only be one subparser_action,
# but better safe than sorry
for subparsers_action in subparsers_actions:
    # get all subparsers and print help
    for choice, subparser in subparsers_action.choices.items():
        print("Subparser '{}'".format(choice))
        print(subparser.format_help())
```

This example should work for python 2.7 and python 3. The example parser is from Python 2.7 documentation on argparse sub-commands.

The only thing left to do is adding a new argument for the complete help, or replacing the built in `-h/--help`.

argparse subparser monolithic help output

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