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   "source": [
    "# Lecture 3C—Plain Text File Reading and Writing"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In this lecture, we will explore reading and writing plain text files.\n",
    "\n",
    "We will learn:\n",
    "\n",
    "- [Read TXT file](#Reading-plain-text-file)\n",
    "- [Write TXT file](#Example-of-writing-plain-text-file:-Diary-logging)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Reading plain text file"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can use `open()` to read and write plain text file. There are 3 modes when opening a file: \n",
    "\n",
    "- `r` for reading.\n",
    "- `w` for over-writing.\n",
    "- `a` for appending."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "👇🏻 Please note that we need to specify `encoding=\"utf-8\"` in Windows for the `open` function."
   ]
  },
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       "['I want to put a ding in the universe.—Steve Jobs',\n",
       " 'Life is 10% what happens to you and 90% how you react to it.—Charles R. Swindoll',\n",
       " \"Family is not an important thing. It's everything.—Michael J. Fox\",\n",
       " \"Nothing is impossible, the word itself says 'I'm possible'!—Audrey Hepburn\",\n",
       " 'There are two ways of spreading light: to be the candle or the mirror that reflects it.—Edith Wharton',\n",
       " \"Try to be a rainbow in someone's cloud.—Maya Angelou\",\n",
       " 'Be brave enough to live life creatively. The creative place where no one else has ever been.—Alan Alda',\n",
       " 'The secret of getting ahead is getting started.—Mark Twain']"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "with open(\"quotes.txt\") as file_obj:\n",
    "    quotes = file_obj.read().splitlines()\n",
    "    \n",
    "quotes"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['I want to put a ding in the universe.—Steve Jobs',\n",
       " 'Life is 10% what happens to you and 90% how you react to it.—Charles R. Swindoll',\n",
       " \"Family is not an important thing. It's everything.—Michael J. Fox\",\n",
       " \"Nothing is impossible, the word itself says 'I'm possible'!—Audrey Hepburn\",\n",
       " 'There are two ways of spreading light: to be the candle or the mirror that reflects it.—Edith Wharton',\n",
       " \"Try to be a rainbow in someone's cloud.—Maya Angelou\",\n",
       " 'Be brave enough to live life creatively. The creative place where no one else has ever been.—Alan Alda',\n",
       " 'The secret of getting ahead is getting started.—Mark Twain']"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "with open(\"quotes.txt\", encoding=\"utf-8\") as file_obj:\n",
    "    quotes = file_obj.read().splitlines()\n",
    "    \n",
    "quotes"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Family is not an important thing. It's everything.—Michael J. Fox\n"
     ]
    }
   ],
   "source": [
    "import random\n",
    "\n",
    "quote = random.choice(quotes)\n",
    "\n",
    "print(quote)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Example of writing plain text file: Diary logging\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "What do you want to say to Mr. Diary? Hello python.\n",
      "2020-06-11: Hello\n",
      "2020-06-11: Hello\n",
      "2020-08-10: Hello python.\n"
     ]
    }
   ],
   "source": [
    "import datetime\n",
    "\n",
    "content = input(\"What do you want to say to Mr. Diary? \")\n",
    "if len(content) > 0:\n",
    "    with open('diary.txt', \"a\") as file_obj:\n",
    "        today = datetime.date.today().isoformat()\n",
    "        file_obj.write(today + \": \" + content + \"\\n\")\n",
    "\n",
    "with open('diary.txt', \"r\") as file_obj:\n",
    "    lines = file_obj.readlines()\n",
    "    for line in lines[-3:]:\n",
    "        print(line.rstrip())\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Summary\n",
    "\n",
    "In this section, we learned to read and write plain text file. "
   ]
  }
 ],
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