An example on how to Parse commands from Slack using argparse

parsing_commands.py

import argparse
import shlex
from typing import List, Optional, TypedDict


class Command(TypedDict):
    prefix: str
    name: str
    args: List[str]


def parse_command(command_text: str) -> Optional[Command]:
    prefix, *args = shlex.split(command_text)

    if not prefix.startswith("/"):
        return None

    parser = argparse.ArgumentParser()

    parser.add_argument("command", type=str, help="The command to execute")
    parser.add_argument("args", nargs="*", help="Additional arguments for the command")

    try:
        options = parser.parse_args(args)
        return Command(prefix=prefix, name=options.command, args=options.args)

    except SystemExit:
        return None


def test_parse_command():
    command_text = '/tesorio create_invoice 123 "Sample Invoice"'
    command = parse_command(command_text)
    assert command == {
        "prefix": "/tesorio",
        "name": "create_invoice",
        "args": ["123", "Sample Invoice"],
    }

    command_text = "/prefix command arg1 arg2 arg3"
    command = parse_command(command_text)
    assert command == {
        "prefix": "/prefix",
        "name": "command",
        "args": ["arg1", "arg2", "arg3"],
    }

    command_text = "/prefix command"
    command = parse_command(command_text)
    assert command == {"prefix": "/prefix", "name": "command", "args": []}

    command_text = "  /prefix command arg1 arg2 'Mi long text with spaces' "
    command = parse_command(command_text)
    assert command == {
        "prefix": "/prefix",
        "name": "command",
        "args": ["arg1", "arg2", "Mi long text with spaces"],
    }

    command_text = "command arg1 arg2"
    command = parse_command(command_text)
    assert command is None

    command_text = "/prefix command arg1 arg2 --invalid-arg"
    command = parse_command(command_text)
    assert command is None

parsing_commands_complete_with_subparsers.py

"""
TODO: Use subparsers to also validate arguments by commands
"""

parser = argparse.ArgumentParser(description='Tesorio Slack Bot')

subparsers = parser.add_subparsers(dest='command')

retrieve_invoice_parser = subparsers.add_parser('invoice', help='Retrieve an invoice')
retrieve_invoice_parser.add_argument('invoice_id', type=int, help='Invoice ID')

retrieve_customer_parser = subparsers.add_parser('customer', help='Retrieve a cutomer summary')
retrieve_customer_parser.add_argument('customer_id', type=int, help='Customer ID')

watch_parser = subparsers.add_parser('watch', help='Watch an invoice')
watch_parser.add_argument('invoice_id', type=int, help='Invoice ID')