project-oop-abstraction-polymorphism.ipynb

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   "source": [
    "# 物件導向程式設計四大支柱之三與四：抽象與多型\n",
    "\n",
    "> 續談第三與第四支柱：抽象（Abstraction）與多型（Polymorphism）。\n",
    ">\n",
    "> 標籤：程式設計\n",
    "\n",
    "郭耀仁 <yaojenkuo@datainpoint.com> from [DATAINPOINT](https://datainpoint.substack.com/welcome)"
   ]
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   "source": [
    "## TL; DR\n",
    "\n",
    "在這個專案中，我們打算使用 Python 自訂三個類別 `AbstractAdd`、`SimpleAdd` 與 `IntermediateAdd`；這三個類別分別都僅具有一個成員方法。透過這個專案，我們能夠暸解何謂物件導向的第三與第四支柱：抽象與多型。"
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   "source": [
    "## 定義 `AbstractAdd` 類別繼承 `ABC` 類別"
   ]
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   "execution_count": 1,
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   "outputs": [
    {
     "ename": "TypeError",
     "evalue": "Can't instantiate abstract class AbstractAdd with abstract methods add",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-1-d936b2844fbd>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      5\u001b[0m     \u001b[0;32mdef\u001b[0m \u001b[0madd\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      6\u001b[0m         \u001b[0;32mpass\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 7\u001b[0;31m \u001b[0maa\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mAbstractAdd\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;31m# Unable to initialize\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mTypeError\u001b[0m: Can't instantiate abstract class AbstractAdd with abstract methods add"
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   "source": [
    "from abc import ABC, abstractmethod\n",
    "\n",
    "class AbstractAdd(ABC):\n",
    "    @abstractmethod\n",
    "    def add(self):\n",
    "        pass\n",
    "aa = AbstractAdd() # Unable to initialize, expecting error"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 定義 `SimpleAdd` 繼承 `AbstractAdd` 類別"
   ]
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   "execution_count": 2,
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     "data": {
      "text/plain": [
       "121"
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   "source": [
    "class SimpleAdd(AbstractAdd):\n",
    "    def add(self, x, y):\n",
    "        return x + y\n",
    "\n",
    "sa = SimpleAdd() # Able to initialize\n",
    "sa.add(55, 66)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 定義 `IntermediateAdd` 繼承 `AbstractAdd` 類別"
   ]
  },
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   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "22"
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     "execution_count": 3,
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   "source": [
    "class IntermediateAdd(AbstractAdd):\n",
    "    def add(self, *args):\n",
    "        return sum(args)\n",
    "\n",
    "ia = IntermediateAdd() # Able to initialize\n",
    "ia.add(5, 5, 6, 6)"
   ]
  }
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