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   "source": [
    "# Tutorial 06: Deriving Evolver and Driver classes\n",
    "\n",
    "> Interactive online tutorial:\n",
    "> [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/ubermag/micromagneticmodel/master?filepath=docs%2Fipynb%2Findex.ipynb)\n",
    "\n",
    "In `micromagneticmodel` package, base classes `micromagneticmodel.Driver` and `micromagneticmodel.Evolver` are defined. Their purpose is to build individual evolvers and drivers in a particular micromagnetic calculator. In this tutorial, we will demonstrate some of their basic properties, on an example of a `micromagneticmodel.Driver` class. The behaviour of the `micromagneticmodel.Evolver` class is the same.\n",
    "\n",
    "Let us derive `MyDriver` class. In order to define it, `_allowed_kwargs` list must be defined. It is a list of strings, which lists the kwargs which are allowed to be passed."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import micromagneticmodel as mm\n",
    "\n",
    "class MyDriver(mm.Driver):\n",
    "    _allowed_kwargs = ['arg1', 'arg2']"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`Driver` class does not require any parameters to be passed at initialisation. If a keyword argument is from `_allowed_kwargs` list, it will be assigned as a class attribute. Otherwise, `AttributeError` will be raised."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "driver = MyDriver(arg1=1, arg2='value')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The attributes are"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "1"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "driver.arg1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'value'"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "driver.arg2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "If we try to pass a keyword argument at initialisation, which is not in the `_allowed_kwargs` list, `AttributeError` is rased:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Exception raised.\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    driver = MyDriver(arg3=1)\n",
    "except AttributeError:\n",
    "    print('Exception raised.')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The main driver method which must be implemented by a derived class is `drive`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Exception raised.\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    driver.drive()\n",
    "except NotImplementedError:\n",
    "    print('Exception raised.')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Other\n",
    "\n",
    "Full description of all existing descriptors can be found in the [API Reference](https://micromagneticmodel.readthedocs.io/en/latest/?badge=latest)."
   ]
  }
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