data-hiding.ipynb

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    "Data Hiding \n",
    "\n",
    "Weakly private methods and attributes have a single underscore at the beginning.\n",
    "This signals that they are private, and shouldn't be used by external code. However, it is mostly only a convention, and does not stop external code from accessing them."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
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     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Queue([1, 2, 3])\n",
      "Queue([0, 1, 2, 3])\n",
      "Queue([0, 1, 2])\n",
      "[0, 1, 2]\n"
     ]
    }
   ],
   "source": [
    "class Queue:\n",
    "  def __init__(self, contents):\n",
    "    self._hiddenlist = list(contents)\n",
    "\n",
    "  def push(self, value):\n",
    "    self._hiddenlist.insert(0, value)\n",
    "   \n",
    "  def pop(self):\n",
    "    return self._hiddenlist.pop(-1)\n",
    "\n",
    "  def __repr__(self):\n",
    "    return \"Queue({})\".format(self._hiddenlist)\n",
    "\n",
    "queue = Queue([1, 2, 3])\n",
    "print(queue)\n",
    "queue.push(0)\n",
    "print(queue)\n",
    "queue.pop()\n",
    "print(queue)\n",
    "print(queue._hiddenlist)"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Strongly private methods and attributes have a double underscore at the beginning of their names. This causes their names to be mangled, which means that they can't be accessed from outside the class. \n",
    "\n",
    "The purpose of this isn't to ensure that they are kept private, but to avoid bugs if there are subclasses that have methods or attributes with the same names.\n",
    "\n",
    "Name mangled methods can still be accessed externally, but by a different name. The method __privatemethod of class Spam could be accessed externally with _Spam__privatemethod."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
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    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "7\n",
      "7\n"
     ]
    },
    {
     "ename": "AttributeError",
     "evalue": "'Spam' object has no attribute '__egg'",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "Cell \u001b[1;32mIn[3], line 9\u001b[0m\n\u001b[0;32m      7\u001b[0m s\u001b[38;5;241m.\u001b[39mprint_egg()\n\u001b[0;32m      8\u001b[0m \u001b[38;5;28mprint\u001b[39m(s\u001b[38;5;241m.\u001b[39m_Spam__egg)\n\u001b[1;32m----> 9\u001b[0m \u001b[38;5;28mprint\u001b[39m(\u001b[43ms\u001b[49m\u001b[38;5;241;43m.\u001b[39;49m\u001b[43m__egg\u001b[49m)\n",
      "\u001b[1;31mAttributeError\u001b[0m: 'Spam' object has no attribute '__egg'"
     ]
    }
   ],
   "source": [
    "class Spam:\n",
    "  __egg = 7\n",
    "  def print_egg(self):\n",
    "    print(self.__egg)\n",
    "\n",
    "s = Spam()\n",
    "s.print_egg()\n",
    "print(s._Spam__egg)\n",
    "print(s.__egg)"
   ]
  },
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   "metadata": {},
   "source": [
    "We are working on a game. Our Player class has name and private _lives attributes.\n",
    "\n",
    "The hit() method should decrease the lives of the player by 1. In case the lives equal to 0, it should output \"Game Over\".\n",
    "\n",
    "Complete the hit() method to make the program work as expected."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Game Over\n"
     ]
    }
   ],
   "source": [
    "class Player:\n",
    "    def __init__(self, name, lives):\n",
    "        self.name = name\n",
    "        self._lives = lives\n",
    "\n",
    "    def hit(self):\n",
    "        self._lives -= 1\n",
    "        if self._lives == 0:\n",
    "            print('Game Over')\n",
    "        #your code goes here\n",
    "        \n",
    "\n",
    "p = Player(\"Cyberpunk77\", 3)\n",
    "p.hit()\n",
    "p.hit()\n",
    "p.hit()\n"
   ]
  }
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