subcmdparse 0.1.10

Subcommand extension for argparse package

subcmdparse

argparse extension for declarative subcommands. Each subcommand is a class with on_parser_init(parser) and on_command(args) hooks; a SubcommandParser ties them together and runs the right one based on sys.argv.

Adds nice-to-haves on top of stock argparse: a --help-all action that prints help for the whole tree, optional argcomplete integration, tolerant subparser dispatch, and allow_unknown_args passthrough.

Python ≥ 3.7. Optional: argcomplete.

Install

pip install -e .

Quick start

from subcmdparse import Subcommand, SubcommandParser


class Greet(Subcommand):
    def on_parser_init(self, parser):
        parser.add_argument("name")
        parser.add_argument("--shout", action="store_true")

    def on_command(self, args):
        msg = f"hello, {args.name}"
        print(msg.upper() if args.shout else msg)


class Echo(Subcommand):
    def on_parser_init(self, parser):
        parser.add_argument("text", nargs="+")

    def on_command(self, args):
        print(" ".join(args.text))


if __name__ == "__main__":
    p = SubcommandParser(prog="demo")
    p.add_subcommands(Greet(), Echo())
    p.exec_subcommands()

$ python demo.py greet Alice --shout
HELLO, ALICE

API

from subcmdparse import Subcommand, SubcommandParser

Subcommand

Base class for a single subcommand. Override:

Hook	Purpose
on_parser_init(self, parser)	Add this subcommand's arguments to its own ArgumentParser.
on_command(self, args, unknown_args=None)	Run when this subcommand is selected. unknown_args is populated when allow_unknown_args=True.
on_exception(self, exc) (optional)	Custom error handler for exceptions raised inside on_command.

Class attributes you can set instead of constructor args: name (CLI name, defaults to class name lowercased), help, description, allow_unknown_args.

Subcommands can themselves contain nested Subcommands — pass them to SubcommandParser.add_subcommands inside a parent's on_parser_init, or expose them via the class's nested-subcommands attribute.

SubcommandParser(*args, argcomplete=False, add_help_all=True, **kwargs)

Subclass of argparse.ArgumentParser.

Method / property	Description
add_subcommands(*subcommands, title=None, required=True, help=None, metavar='SUBCOMMAND')	Register one or more Subcommand instances.
parse_args(...)	As in argparse; also registers pending subcommands and runs argcomplete.
exec_subcommands(parsed_args=None)	Parse args (if not given) and dispatch to the selected subcommand's on_command.
add_help (read/write)	Enable/disable the standard -h/--help after construction.
allow_unknown_args (read/write)	When True, unrecognised args are passed to on_command instead of erroring.
argcomplete	When True, calls argcomplete.autocomplete(self) during parse_args.
add_help_all	When True (default), exposes --help-all which prints help for every subcommand recursively.