CLI Argument Parser Implementation

[
  {
    "argv": [
      "create",
      "--source",
      "/data"
    ],
    "outcome": "success",
    "expected_namespace": {
      "command": "create",
      "source": "/data",
      "compress": false
    }
  },
  {
    "argv": [
      "create",
      "--source",
      "/data",
      "--compress"
    ],
    "outcome": "success",
    "expected_namespace": {
      "command": "create",
      "source": "/data",
      "compress": true
    }
  },
  {
    "argv": [
      "restore",
      "--archive",
      "a.tar"
    ],
    "outcome": "success",
    "expected_namespace": {
      "command": "restore",
      "archive": "a.tar",
      "target": null
    }
  },
  {
    "argv": [
      "restore",
      "--archive",
      "a.tar",
      "--target",
      "/restore"
    ],
    "outcome": "success",
    "expected_namespace": {
      "command": "restore",
      "archive": "a.tar",
      "target": "/restore"
    }
  },
  {
    "argv": [],
    "outcome": "failure",
    "expected_exit_code": 2,
    "expected_error_substring": "required"
  },
  {
    "argv": [
      "create"
    ],
    "outcome": "failure",
    "expected_exit_code": 2,
    "expected_error_substring": "required"
  },
  {
    "argv": [
      "bogus"
    ],
    "outcome": "failure",
    "expected_exit_code": 2,
    "expected_error_substring": "invalid choice"
  }
]

import argparse

def build_parser():
    p = argparse.ArgumentParser(prog="backupctl")
    sub = p.add_subparsers(dest="command", required=True)

    create_p = sub.add_parser("create")
    create_p.add_argument("--source", required=True)
    create_p.add_argument("--compress", action="store_true", default=False)

    restore_p = sub.add_parser("restore")
    restore_p.add_argument("--archive", required=True)
    restore_p.add_argument("--target", default=None)

    return p

A backup CLI tool "backupctl" with subcommands `create` and `restore` (use add_subparsers(dest="command", required=True)). The `create` subcommand takes --source (required string) and --compress (store_true flag, default False). The `restore` subcommand takes --archive (required string) and --target (optional string, default None).