PYTHON-BASIC-4-CONDITION-LOOP-EXCEPTION.ipynb

{
 "cells": [
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   "cell_type": "markdown",
   "metadata": {
    "collapsed": true,
    "slideshow": {
     "slide_type": "slide"
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   },
   "source": [
    "## 조건문"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
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   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "False\n",
      "True\n",
      "False\n",
      "True\n"
     ]
    }
   ],
   "source": [
    "x = 2\n",
    "\n",
    "# 참 거짓을 판단하는 표현식들\n",
    "print(x == 2)\n",
    "print(x == 3)\n",
    "print(x < 3)\n",
    "print(x > 1 and x > 2)\n",
    "print(x > 1 or x > 2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "True\n",
      "Two!\n"
     ]
    }
   ],
   "source": [
    "x = 2\n",
    "print(x > 1 and x < 3)\n",
    "\n",
    "# pythonic\n",
    "print(1 < x < 3)\n",
    "\n",
    "# if statement\n",
    "if 1 < x < 3:\n",
    "    print('Two!')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Your name is John, and you are also 23 years old.\n"
     ]
    }
   ],
   "source": [
    "name = \"John\"\n",
    "age = 23\n",
    "\n",
    "# and 연산\n",
    "if name == \"John\" and age == 23:\n",
    "    print(\"Your name is John, and you are also 23 years old.\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Your name is either John or Rick.\n",
      "Your name is either John or Rick.\n"
     ]
    }
   ],
   "source": [
    "name = \"John\"\n",
    "\n",
    "# or 연산\n",
    "if name == \"John\" or name == \"Rick\":\n",
    "    print(\"Your name is either John or Rick.\")\n",
    "\n",
    "# Pythonic\n",
    "if name in [\"John\", \"Rick\"]:\n",
    "    print(\"Your name is either John or Rick.\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "x equals two!\n"
     ]
    }
   ],
   "source": [
    "x = 2\n",
    "\n",
    "# if - else\n",
    "if x == 2:\n",
    "    print(\"x equals two!\")\n",
    "else:\n",
    "    print(\"x does not equal to two.\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "False\n",
      "True\n",
      "True\n"
     ]
    }
   ],
   "source": [
    "# equal, is\n",
    "\n",
    "x = [1,2,3]\n",
    "y = [1,2,3]\n",
    "print(x == y)\n",
    "print(x is y)  # is는 id가 같은 객체를 판단한다고 생각하면 됩니다\n",
    "print(None is None)\n",
    "print(x is not y)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "False\n"
     ]
    }
   ],
   "source": [
    "print(not False) # Prints out True\n",
    "print((not False) == (False)) # Prints out False"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "다음과 같은 줄임버전을 사용할 수 있습니다."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "number = -2\n",
    "new_number = number if number >= 0 else 0\n",
    "# c, java에서 선호되던 이 방식은 지원하지 않습니다.\n",
    "# new_number = (number > = 0)?number:0\n",
    "new_number"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "number = -10\n",
    "new_number = number if number >= 0 else 0\n",
    "new_number"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "not은 읽기 좋은 곳에 두는 것이 좋습니다."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "set!\n",
      "set also!\n"
     ]
    }
   ],
   "source": [
    "d = {'key': 'val'}\n",
    "if d.get('key') is not None:  # good\n",
    "    print('set!')\n",
    "if not d.get('key') is None:  # bad\n",
    "    print('set also!')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "(condition) 관행적으로 True, False 테스트는 <span class=\"mark\">비교구문없이 값만으로</span> 하는것을 선호합니다."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "We have pets\n",
      "We have pets\n"
     ]
    }
   ],
   "source": [
    "name = 'Safe'\n",
    "pets = ['Dog', 'Cat', 'Hamster']\n",
    "owners = {'Safe': 'Cat', 'Geroge': 'Dog'}\n",
    "\n",
    "if name and pets and owners: # good\n",
    "    print('We have pets')\n",
    "\n",
    "if (name != '' or len(name)) and len(pets) > 0 and owners != {}: # bad\n",
    "    print('We have pets')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "(condition) 가급적 in으로 해결합니다."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "H is found!\n",
      "H is found!\n"
     ]
    }
   ],
   "source": [
    "name = 'Safe Hammad'\n",
    "if name.find('H') != -1:\n",
    "    print('H is found!')\n",
    "if 'H' in name:\n",
    "    print('H is found!')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hello\n",
      "world\n",
      "world\n",
      "world\n"
     ]
    }
   ],
   "source": [
    "# 재미있는 시도\n",
    "print(None or \"hello\")\n",
    "print(\"hello\" and \"world\")\n",
    "\n",
    "d = {}\n",
    "print(d.get('hello') or 'world')\n",
    "print(d.get('hello', 'world'))\n",
    "\n",
    "d = {'hello': None}\n",
    "x = d.get('hello', '') or ''"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## EXERCISE"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "ename": "TypeError",
     "evalue": "'>' not supported between instances of 'NoneType' and 'int'",
     "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-b636ec06e48c>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      7\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      8\u001b[0m \u001b[0;31m# 1-6까지 모두 출력되는 테스트 코드. 그러므로 아래는 건드리지 마세요.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 9\u001b[0;31m \u001b[0;32mif\u001b[0m \u001b[0mnumber\u001b[0m \u001b[0;34m>\u001b[0m \u001b[0;36m15\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     10\u001b[0m     \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"1\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     11\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;31mTypeError\u001b[0m: '>' not supported between instances of 'NoneType' and 'int'"
     ]
    }
   ],
   "source": [
    "# 모두 True가 되도록 아래 코드를 바꿔봅시다.\n",
    "\n",
    "number = None\n",
    "second_number = None\n",
    "first_array = []\n",
    "second_array = []\n",
    "\n",
    "# 1-6까지 모두 출력되는 테스트 코드. 그러므로 아래는 건드리지 마세요. \n",
    "if number > 15:\n",
    "    print(\"1\")\n",
    "\n",
    "if first_array:\n",
    "    print(\"2\")\n",
    "\n",
    "if len(second_array) == 2:\n",
    "    print(\"3\")\n",
    "\n",
    "if len(first_array) + len(second_array) == 5:\n",
    "    print(\"4\")\n",
    "\n",
    "if first_array and first_array[0] == 1:\n",
    "    print(\"5\")\n",
    "\n",
    "if not second_number:\n",
    "    print(\"6\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## LOOP"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "2\n",
      "3\n",
      "5\n",
      "7\n"
     ]
    }
   ],
   "source": [
    "primes = [2, 3, 5, 7]\n",
    "for prime in primes:\n",
    "    print(prime)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 1 2 3 4 \n",
      "3 4 5 \n",
      "3 5 7 \n",
      "5 4 3 2 1 \n"
     ]
    }
   ],
   "source": [
    "# range 함수와 같이 사용하는 경우가 많습니다.\n",
    "for x in range(5):\n",
    "    print(x, end=' ')\n",
    "print()\n",
    "\n",
    "for x in range(3, 6):\n",
    "    print(x, end=' ')\n",
    "print()\n",
    "\n",
    "for x in range(3, 8, 2):\n",
    "    print(x, end=' ')\n",
    "print()\n",
    "\n",
    "for x in range(5, 0, -1):\n",
    "    print(x, end=' ')\n",
    "print()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "1\n",
      "2\n",
      "3\n",
      "4\n"
     ]
    }
   ],
   "source": [
    "# Prints out 0,1,2,3,4\n",
    "\n",
    "count = 0\n",
    "while count < 5:\n",
    "    print(count)\n",
    "    count += 1  # This is the same as count = count + 1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0, 1, 2, 3, 4, \n",
      "1, 3, 5, 7, 9, "
     ]
    }
   ],
   "source": [
    "# continue, break\n",
    "count = 0\n",
    "while True:\n",
    "    print(count, end=', ')\n",
    "    count += 1\n",
    "    if count >= 5:\n",
    "        break\n",
    "print()\n",
    "\n",
    "for x in range(10):\n",
    "    # Check if x is even\n",
    "    if x % 2 == 0:\n",
    "        continue\n",
    "    print(x, end=', ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 1 2 3 4 count value reached 5\n",
      "1 2 3 4 "
     ]
    }
   ],
   "source": [
    "# else\n",
    "count=0\n",
    "while(count<5):\n",
    "    print(count, end=' ')\n",
    "    count +=1\n",
    "else:\n",
    "    print(\"count value reached %d\" %(count))\n",
    "\n",
    "for i in range(1, 10):\n",
    "    if(i%5==0):\n",
    "        break\n",
    "    print(i, end=' ')\n",
    "else:\n",
    "    print(\"this is not printed because for loop is terminated because of break but not due to fail in condition\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "내 100은 어디에 있나요?\n"
     ]
    }
   ],
   "source": [
    "found = False\n",
    "for i in range(100):\n",
    "    if i == 100:\n",
    "        found = True\n",
    "        break\n",
    "\n",
    "if not found:\n",
    "    print('내 100은 어디에 있나요?')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "내 100은 어디에 있나요?\n"
     ]
    }
   ],
   "source": [
    "for i in range(100):\n",
    "    if i == 100:\n",
    "        break\n",
    "else:\n",
    "    print('내 100은 어디에 있나요?')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "*그러나 loop문의 else는 가독성면에서 혼란을 야기한다는 이유로 잘 사용하지 않습니다.*"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 tic\n",
      "1 tac\n",
      "2 toe\n",
      "0 tic\n",
      "1 tac\n",
      "2 toe\n"
     ]
    }
   ],
   "source": [
    "# index를 함께 보고 싶을 때\n",
    "a = ['tic', 'tac', 'toe']\n",
    "for i in range(len(a)):\n",
    "    print(i, a[i])\n",
    "for i, v in enumerate(a):\n",
    "    print(i, v)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hello\n",
      "world\n",
      "hello 1\n",
      "world 2\n"
     ]
    }
   ],
   "source": [
    "# dictionary를 loop하고 싶을 때\n",
    "d = {'hello': 1, 'world': 2}\n",
    "for k in d:\n",
    "    print(k)\n",
    "for key, value in d.items():\n",
    "    print(key, value)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1 2 3 3 2 1 "
     ]
    }
   ],
   "source": [
    "# 정렬하거나, 뒤집거나\n",
    "for k in sorted([3,1,2]):\n",
    "    print(k, end= ' ')\n",
    "for k in reversed(sorted([3,1,2])):\n",
    "    print(k, end= ' ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "t h a n k y o u "
     ]
    }
   ],
   "source": [
    "# 문자열을 loop하면\n",
    "for char in \"thankyou\":\n",
    "    print(char, end=' ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "total 3672\n",
      "drwxr-xr-x@  4 happytk  staff      136 May 17 22:09 .\n",
      "drwx------@ 49 happytk  staff     1666 May 17 22:08 ..\n",
      "-rwxr-xr-x@  1 happytk  staff  1877810 May 12 18:46 WindowsUpdate.log\n",
      "-rw-r--r--   1 happytk  staff        0 May 17 22:09 myfile.txt\n",
      "total 3672\n",
      "drwxr-xr-x@  4 happytk  staff      136 May 17 22:09 .\n",
      "drwx------@ 49 happytk  staff     1666 May 17 22:08 ..\n"
     ]
    }
   ],
   "source": [
    "for line in open('data/myfile.txt'):\n",
    "    print(line, end='')\n",
    "\n",
    "# 3줄만? -- 중급에서 만나요.\n",
    "from itertools import islice\n",
    "for line in islice(open('data/myfile.txt'), 3):\n",
    "    print(line, end='')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## 연습문제"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [],
   "source": [
    "numbers = [\n",
    "    951, 402, 984, 651, 360, 69, 408, 319, 601, 485, 980, 507, 725, 547, 544,\n",
    "    615, 83, 165, 141, 501, 263, 617, 865, 575, 219, 390, 984, 592, 236, 105, 942, 941,\n",
    "    386, 462, 47, 418, 907, 344, 236, 375, 823, 566, 597, 978, 328, 615, 953, 345,\n",
    "    399, 162, 758, 219, 918, 237, 412, 566, 826, 248, 866, 950, 626, 949, 687, 217,\n",
    "    815, 67, 104, 58, 512, 24, 892, 894, 767, 553, 81, 379, 843, 831, 445, 742, 717,\n",
    "    958, 609, 842, 451, 688, 753, 854, 685, 93, 857, 440, 380, 126, 721, 328, 753, 470,\n",
    "    743, 527, 1, 0\n",
    "]\n",
    "\n",
    "# 01. 두자리 숫자만 출력해보세요.\n",
    "\n",
    "# 02. 숫자의 첫자리가 7인 경우만 출력해보세요.\n",
    "\n",
    "# 03. 숫자가 84로 시작하는 경우만 출력해보세요.\n",
    "\n",
    "# 04. 숫자가 23으로 끝나는 경우만 출력해보세요.\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## EXCEPTION "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "ename": "NameError",
     "evalue": "name 'a' is not defined",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-9-c5a4f3535135>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0ma\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mNameError\u001b[0m: name 'a' is not defined"
     ]
    }
   ],
   "source": [
    "print(a)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "잡았습니다.\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    print(a)\n",
    "except NameError:\n",
    "    print('잡았습니다.')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "여러개의 exception을 잡을 수 있습니다.(PEP 3110)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "여러개를 잡아요.\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    print(a)\n",
    "except (NameError, IndexError):   \n",
    "    print('여러개를 잡아요.')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "여러개를 잡아요. -> name 'a' is not defined\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    print(a)\n",
    "except (NameError, IndexError) as e:\n",
    "    print('여러개를 잡아요. ->', e)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "pyenv-implicit: found multiple python2 in pyenv. Use version 2.7.12.\n",
      "Traceback (most recent call last):\n",
      "  File \"<stdin>\", line 3, in <module>\n",
      "IndexError: list index out of range\n"
     ]
    }
   ],
   "source": [
    "%%python2\n",
    "try:\n",
    "    l = [\"a\", \"b\"]\n",
    "    int(l[2])\n",
    "except NameError, IndexError:  # python3에서는 어차피 안되지만.\n",
    "    pass"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "KeyError를처리해요.\n"
     ]
    }
   ],
   "source": [
    "# 여러개의 exception을 나누어서 처리하기\n",
    "try:\n",
    "    print({}['a'])\n",
    "    print(a)\n",
    "except NameError:\n",
    "    print('NameError를처리해요.')\n",
    "except KeyError:\n",
    "    print('KeyError를처리해요.')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "source": [
    "exception을 만들어 낼 수도 (던질 수도) 있어요. (PEP 3109)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "ename": "Exception",
     "evalue": "error-message",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mException\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-19-888a574ca470>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[1;32mraise\u001b[0m \u001b[0mException\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;34m'error-message'\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mException\u001b[0m: error-message"
     ]
    }
   ],
   "source": [
    "raise Exception('error-message')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "key does not exist.\n"
     ]
    },
    {
     "ename": "KeyError",
     "evalue": "'a'",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mKeyError\u001b[0m                                  Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-1-692a4bf142e4>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# reraise\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m     \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m{\u001b[0m\u001b[0;34m}\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0;34m'a'\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      4\u001b[0m \u001b[0;32mexcept\u001b[0m \u001b[0mKeyError\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m     \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'key does not exist.'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;31mKeyError\u001b[0m: 'a'"
     ]
    }
   ],
   "source": [
    "# reraise\n",
    "try:\n",
    "    print({}['a'])\n",
    "except KeyError:\n",
    "    print('key does not exist.')\n",
    "    raise"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "구체적으로 잡고, 구체적으로 던지세요!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "var1 = 1\n",
    "try:\n",
    "    do_something(var2)\n",
    "except:  # bad-case\n",
    "    pass"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "흐름제어를 좀 더 세세하게!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "반드시 처리해야 하는 구문\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    print('')\n",
    "except NameError:\n",
    "    print('NameError를처리해요.')\n",
    "finally:\n",
    "    print('반드시 처리해야 하는 구문')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "에러를 처리해요.\n",
      "반드시 처리해야 하는 구문\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    print(a)\n",
    "except NameError:\n",
    "    print('에러를 처리해요.')\n",
    "else:\n",
    "    print('에러없이 끝났을 경우')\n",
    "finally:\n",
    "    print('반드시 처리해야 하는 구문')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "*마찬가지로 try-catch문의 else도 가독성면에서 혼란을 야기한다는 이유로 잘 사용하지 않습니다.*"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1, 2, 3, 4, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "
     ]
    }
   ],
   "source": [
    "def do_stuff_with_number(n):\n",
    "        print(n, end=', ')\n",
    "\n",
    "the_list = (1, 2, 3, 4, 5)\n",
    "\n",
    "for i in range(20):\n",
    "    try:\n",
    "        do_stuff_with_number(the_list[i])\n",
    "    except IndexError: # Raised when accessing a non-existing index of a list\n",
    "        do_stuff_with_number(0)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## EXERCISE"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "All exceptions caught! Good job!\n",
      "The actor's last name is None\n"
     ]
    }
   ],
   "source": [
    "# 다음 코드에서 발생하는 모든 예외를 처리하세요\n",
    "actor = {\"name\": \"John Cleese\", \"rank\": \"awesome\", \"last_name\": \"Cleese\"}\n",
    "\n",
    "# quiz) actor의 last_name이 있으면 처리하고 없으면 name에서 last_name을 가져오도록 수정해주세요.\n",
    "def get_last_name():\n",
    "    # 도전) if문을 썼다면 제거해보세요\n",
    "    pass\n",
    "\n",
    "\n",
    "# Test code (여기서부터는 수정하지 마세요)\n",
    "get_last_name()\n",
    "print(\"All exceptions caught! Good job!\")\n",
    "print(\"The actor's last name is %s\" % get_last_name())"
   ]
  }
 ],
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