{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# The python exercises\n",
    "\n",
    "**Ex 0**: The Jupyter Notebooks are organized as a list of cells. There are two central kinds of cells, they are called **Code** and **Markdown**. The cell type can be set [using a keyboard shortcut](https://www.dataquest.io/blog/jupyter-notebook-tips-tricks-shortcuts/), or using the menus above.\n",
    "\n",
    "The **Code** cells simply contain the Python code, no big deal.\n",
    "\n",
    "The **Markdown** cells contain text (explanations, sections, etc). The text is written in Markdown. Markdown allows you to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML). You can read about it here:\n",
    "\n",
    "http://daringfireball.net/projects/markdown/\n",
    "\n",
    "In the cell below, write a short text that demonstrates that you can\n",
    "* Create a section\n",
    "* Write words in bold and italics\n",
    "* Create lists\n",
    "* Establish a [hyperlink](https://en.wikipedia.org/wiki/Hyperlink)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "*[Write the answer to **Ex 0** here]*"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 1**: Create a list `a` that contains the numbers from $1$ to $1110$, incremented by one, using the `range` function."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 2**: Show that you understand [slicing](http://stackoverflow.com/questions/509211/explain-pythons-slice-notation) in Python by extracting a list `b` with the numbers from $543$ to $779$ from the list created above."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 3**: Using `def`, define a function that takes as input a number $x$ and outputs the number multiplied by itself plus three $f(x) = x(x+3)$. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 4**: Apply this function to every element of the list `b` using a `for` loop. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 5**: Do the same thing using a list comprehension."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 6**: Write the output of your function to a text file with one number per line."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 7**: Show that you know about strings using this example from http://learnpythonthehardway.org/book/ex6.html (code reproduced below).\n",
    "\n",
    "1. Go through the code below and write a code comment above each line explaining it.\n",
    "1. Find all the places where a string is put inside a string. There are four places.\n",
    "1. Are you sure there are only four places? How do you know? Maybe I like lying.\n",
    "1. Explain why adding the two strings w and e with + makes a longer string.\n",
    "\n",
    "\n",
    "[**Hint**: If you feel this is too complex, try completing the prior learningthehardway exercises first. Start [here](http://learnpythonthehardway.org/book/ex1.html). "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "There are 10 types of people.\n",
      "Those who know binary and those who don't.\n",
      "I said: 'There are 10 types of people.'.\n",
      "I also said: 'Those who know binary and those who don't.'.\n",
      "Isn't that joke so funny?! False\n",
      "This is the left side of...a string with a right side.\n"
     ]
    }
   ],
   "source": [
    "# Note from Sune: In Python, code comments follow the \"#\" character\n",
    "\n",
    "x = \"There are %d types of people.\" % 10\n",
    "binary = \"binary\"\n",
    "do_not = \"don't\"\n",
    "y = \"Those who know %s and those who %s.\" % (binary, do_not)\n",
    "\n",
    "print x\n",
    "print y\n",
    "\n",
    "print \"I said: %r.\" % x\n",
    "print \"I also said: '%s'.\" % y\n",
    "\n",
    "hilarious = False\n",
    "joke_evaluation = \"Isn't that joke so funny?! %r\"\n",
    "\n",
    "print joke_evaluation % hilarious\n",
    "\n",
    "w = \"This is the left side of...\"\n",
    "e = \"a string with a right side.\"\n",
    "\n",
    "print w + e"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "*[Write the answer to **Ex 7**, 2-4 here]*"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 8**: First, learn about JSON by reading the **[wikipedia page](https://en.wikipedia.org/wiki/JSON)**. Then answer the following two questions in the cell below. \n",
    "\n",
    "* What is `json`? What do the letters stand for?\n",
    "* Why is `json` superior to `xml`? (... or why not?)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "*[Write your answer to **Ex 8** here]*"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 9a**: Use the `json` module (instructions on usage here: https://docs.python.org/2.7/library/json.html). \n",
    "\n",
    "First use `urllib2` (https://docs.python.org/2.7/howto/urllib2.html), or another Python library, to download **[this file](https://raw.githubusercontent.com/suneman/socialgraphs2016/master/files/test.json)**. \n",
    "\n",
    "The downloaded file is a string when you first download it, but you can use the `json` library to \"load\" the string and decode it to a Python object, using `json.loads()`. (The decoded string is a python object, a list with a single element, a dictionary (with nested dictionaries inside it))."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 9b**: Now, let's take a look at the file you downloaded. First, just write the name of the variable that contains the decoded file content and hit enter to take a look at it. It's  the list of Twitter Trending topics, a few days ago."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 9c**: The thing you've just decoded is now a list of length 1. What are the names of the keys organizing the dictionary at position 0 in the list? (Just write the code to produce the answer.) \n",
    "\n",
    "**Hint** use the `.keys()` method to easily get the keys of any dictionary."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 9d**: Two small questions \n",
    "* What time did I create the list of Trending Topics?\n",
    "* Print the names of the trending topics (bonus for using a list comprehension)\n",
    "\n",
    "(Just write the code to produce the answer.)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Ex 9e**: Two more small questions\n",
    "* Go on-line and figure out why there's a `u` in front of every string. Write the answer in your own words. (Hint it has to do with strings in Python).\n",
    "* What's going on with all of the `%22` and `%23`? Go on-line and figure it out. Write the answer in your own words. (Hint: It has to do with HTML URL encoding)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "*[Write your answer to **Ex 9e** here]*"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  }
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