Factory Method Design Pattern in Python and it's Implementations

classic.ipynb

object_factory_and_service_provider.ipynb

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   "cell_type": "markdown",
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   "source": [
    "# Example of Factory Design Patter using ObjectFactory and ServiceProvider"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Example is based on article from https://realpython.com/factory-method-python/"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Each builder has required parameters, and ignores any additional parameters provided through **_ignored"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "class SpotifyService:\n",
    "    def __init__(self, access_code):\n",
    "        self._access_code = access_code\n",
    "\n",
    "    def test_connection(self):\n",
    "        print(f'Accessing Spotify with {self._access_code}')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
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   "source": [
    "class SpotifyServiceBuilder:\n",
    "    def __init__(self):\n",
    "        self._instance = None\n",
    "\n",
    "    def __call__(self, spotify_client_key, spotify_client_secret, **_ignored):\n",
    "        if not self._instance:\n",
    "            access_code = self.authorize(\n",
    "                spotify_client_key, spotify_client_secret)\n",
    "            self._instance = SpotifyService(access_code)\n",
    "        return self._instance\n",
    "\n",
    "    def authorize(self, key, secret):\n",
    "        return 'SPOTIFY_ACCESS_CODE'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "class PandoraService:\n",
    "    def __init__(self, consumer_key, consumer_secret):\n",
    "        self._key = consumer_key\n",
    "        self._secret = consumer_secret\n",
    "\n",
    "    def test_connection(self):\n",
    "        print(f'Accessing Pandora with {self._key} and {self._secret}')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [],
   "source": [
    "class PandoraServiceBuilder:\n",
    "    def __init__(self):\n",
    "        self._instance = None\n",
    "\n",
    "    def __call__(self, pandora_client_key, pandora_client_secret, **_ignored):\n",
    "        if not self._instance:\n",
    "            consumer_key, consumer_secret = self.authorize(\n",
    "                pandora_client_key, pandora_client_secret)\n",
    "            self._instance = PandoraService(consumer_key, consumer_secret)\n",
    "        return self._instance\n",
    "\n",
    "    def authorize(self, key, secret):\n",
    "        return 'PANDORA_CONSUMER_KEY', 'PANDORA_CONSUMER_SECRET'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "class LocalService:\n",
    "    def __init__(self, location):\n",
    "        self._location = location\n",
    "\n",
    "    def test_connection(self):\n",
    "        print(f'Accessing Local music at {self._location}')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [],
   "source": [
    "def create_local_music_service(local_music_location, **_ignored):\n",
    "    return LocalService(local_music_location)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## ObjectFactory"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [],
   "source": [
    "class ObjectFactory:\n",
    "    def __init__(self):\n",
    "        self._builders = {}\n",
    "\n",
    "    def register_builder(self, key, builder):\n",
    "        self._builders[key] = builder\n",
    "\n",
    "    def create(self, key, **kwargs):\n",
    "        builder = self._builders.get(key)\n",
    "        if not builder:\n",
    "            raise ValueError(key)\n",
    "        return builder(**kwargs)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## ServiceProvider"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [],
   "source": [
    "class MusicServiceProvider(ObjectFactory):\n",
    "    def get(self, service_id, **kwargs):\n",
    "        return self.create(service_id, **kwargs)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [],
   "source": [
    "services = MusicServiceProvider()\n",
    "services.register_builder('SPOTIFY', SpotifyServiceBuilder())\n",
    "services.register_builder('PANDORA', PandoraServiceBuilder())\n",
    "services.register_builder('LOCAL', create_local_music_service)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [],
   "source": [
    "config = {\n",
    "    'spotify_client_key': 'THE_SPOTIFY_CLIENT_KEY',\n",
    "    'spotify_client_secret': 'THE_SPOTIFY_CLIENT_SECRET',\n",
    "    'pandora_client_key': 'THE_PANDORA_CLIENT_KEY',\n",
    "    'pandora_client_secret': 'THE_PANDORA_CLIENT_SECRET',\n",
    "    'local_music_location': '/usr/data/music'\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Accessing Pandora with PANDORA_CONSUMER_KEY and PANDORA_CONSUMER_SECRET\n",
      "Accessing Spotify with SPOTIFY_ACCESS_CODE\n",
      "Accessing Local music at /usr/data/music\n",
      "id(pandora) == id(pandora2): True\n",
      "id(spotify) == id(spotify2): True\n"
     ]
    }
   ],
   "source": [
    "pandora = services.get('PANDORA', **config)\n",
    "pandora.test_connection()\n",
    "\n",
    "spotify = services.get('SPOTIFY', **config)\n",
    "spotify.test_connection()\n",
    "\n",
    "local = services.get('LOCAL', **config)\n",
    "local.test_connection()\n",
    "\n",
    "pandora2 = services.get('PANDORA', **config)\n",
    "print(f'id(pandora) == id(pandora2): {id(pandora) == id(pandora2)}')\n",
    "\n",
    "spotify2 = services.get('SPOTIFY', **config)\n",
    "print(f'id(spotify) == id(spotify2): {id(spotify) == id(spotify2)}')"
   ]
  }
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