0026 Retrieving from dicts with dict.get.ipynb

{
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     "execution_count": 1,
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   "source": [
    "d = {'a':1, 'b':2, 'c':3}\n",
    "\n",
    "d['a']"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "ename": "KeyError",
     "evalue": "'x'",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mKeyError\u001b[0m                                  Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-2-7657742692bd>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0md\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0;34m'x'\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mKeyError\u001b[0m: 'x'"
     ]
    }
   ],
   "source": [
    "d['x']"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter a key: a\n",
      "d[a] == 1\n",
      "Enter a key: b\n",
      "d[b] == 2\n",
      "Enter a key: c\n",
      "d[c] == 3\n",
      "Enter a key: d\n",
      "d is not a key in d\n",
      "Enter a key: \n"
     ]
    }
   ],
   "source": [
    "while True:\n",
    "    k = input(\"Enter a key: \").strip()\n",
    "    \n",
    "    if not k:\n",
    "        break\n",
    "        \n",
    "    elif k in d:\n",
    "        print(f'd[{k}] == {d[k]}')\n",
    "        \n",
    "    else:\n",
    "        print(f'{k} is not a key in d')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "1"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "d.get('a')  # if 'a' in d, then give me d['a']"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "d.get('x')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "x is not a key in d\n"
     ]
    }
   ],
   "source": [
    "result = d.get('x')\n",
    "\n",
    "if result is None:\n",
    "    print('x is not a key in d')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'no such key'"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "d.get('x', 'no such key')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "d.get('x', 0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "12345"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "d.get('x', 12345)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'http://python.org/'"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "user_options = {'a':1, 'b':2, 'c':3}\n",
    "\n",
    "user_options.get('profile_page', 'http://python.org/')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'http://lerner.co.il'"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "user_options = {'a':1, 'b':2, 'c':3, \n",
    "                'profile_page':'http://lerner.co.il'}\n",
    "\n",
    "user_options.get('profile_page', 'http://python.org/')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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