chapters/Chapter 6 - Sets.ipynb

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    "# Sets\n",
    "\n",
    "A set is a collection of things, like a list, but the collection is both unordered, and contains no duplicate elements. \n",
    "\n",
    "## General Syntax\n",
    "\n",
    "```python\n",
    "my_numbers = {1, 2, 3, 4}\n",
    "my_letters = {'a', 'b', 'c', 'd'}\n",
    "```\n",
    "\n",
    "Sets are recognizable by their **_curly braces_**, like a **_dictionary_**.\n",
    "Lists have **_square brackets_**, tuples have **_parenthesis_**, sets have **_curly braces_**.\n",
    "\n",
    "The syntactical difference between a set and a dictionary is that sets do not have _keys_ and _values_ , only _values_.\n",
    "\n",
    "```python\n",
    "my_set = {1, 2, 3, 4}\n",
    "my_dictionary = {'key_1': 1, 'key_2': 2, 'key_3': 3, 'key_4': 4}\n",
    "```"
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    "### YOUR TURN\n",
    "\n",
    "* Create a set for _boolean_ values (True and False)\n",
    "* Create another set for even numbers through ten.\n",
    "* Then, print them out. \n",
    "* Print out the type!"
   ]
  },
  {
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   "source": [
    "# Create your sets here"
   ]
  },
  {
   "cell_type": "code",
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   "outputs": [],
   "source": [
    "# Print the results here"
   ]
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    "---\n",
    "\n",
    "## Why use a set?\n",
    "\n",
    "There are a few reasons why you might want to use a set!\n",
    "\n",
    "### 1. Keeping track of _distinct_ values. \n",
    "\n",
    "What are all the unique names in a class?\n",
    "What are the different categories that show up in a collection of things?\n",
    "\n",
    "Let's do an example. "
   ]
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    "class_names = [\n",
    "    'steve',\n",
    "    'ann',\n",
    "    'carol',\n",
    "    'steve',\n",
    "    'bridgette',\n",
    "    'sam',\n",
    "    'kyle'\n",
    "]"
   ]
  },
  {
   "cell_type": "code",
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   "source": [
    "# How many students are in the class?\n",
    "\n",
    "class_size = len(class_names)\n",
    "print(class_size)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# How many distinct students are in the class?\n",
    "\n",
    "distinct_names = set(class_names)\n",
    "distinct_names_size = len(distinct_names)\n",
    "print(distinct_names_size)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "--- \n",
    "\n",
    "### YOUR TURN\n",
    "\n",
    "* Create a list of colors! Make sure there are some duplicate values. \n",
    "* Print out the size of the color list.\n",
    "* Convert your color list to a color set.\n",
    "* Print out the size again\n",
    "* Print out the values of your new set"
   ]
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   "source": [
    "--- \n",
    "\n",
    "### 2. Performing Set Operations!\n",
    "\n",
    "Remember talking about set operations in SQL??\n",
    "Python sets have the same functionality.\n",
    "Here's a quick refresher.\n",
    "\n",
    "![Set Operations](./images/set_operations.png)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "---\n",
    "\n",
    "## Union\n",
    "\n",
    "![Union](images/union.png)\n",
    "\n",
    "Unions are used to _combine_ two or more sets! \n",
    "You would use this when you want to find the shared values between collections.\n",
    "\n",
    "There are a couple ways to perform a union using sets."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "set_1 = {1, 2, 3, 4}\n",
    "set_2 = {3, 4, 5, 6}"
   ]
  },
  {
   "cell_type": "markdown",
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   "source": [
    "First way! \n",
    "With the `.union()` method."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
   "source": [
    "union_set = set_1.union(set_2)\n",
    "print(union_set)"
   ]
  },
  {
   "cell_type": "markdown",
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   "source": [
    "The other way!\n",
    "Use the `|` character.\n",
    "Kind of weird, but saves from some typing!"
   ]
  },
  {
   "cell_type": "code",
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   "source": [
    "union_set = set_1 | set_2\n",
    "print(union_set)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "---\n",
    "\n",
    "## Intersection\n",
    "\n",
    "![Union](images/intersection.png)\n",
    "\n",
    "Intersections are used to find the values common to the sets involved.\n",
    "\n",
    "Like unions, there are a couple ways to perform a union using sets."
   ]
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  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "set_1 = {1, 2, 3, 4}\n",
    "set_2 = {3, 4, 5, 6}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "First way! \n",
    "With the `.intersection()` method."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "intersection_set = set_1.intersection(set_2)\n",
    "print(intersection_set)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The other way!\n",
    "Use the `&` character.\n",
    "Kind of weird, but saves from some typing!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "intersection_set = set_1 & set_2\n",
    "print(intersection_set)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "---\n",
    "\n",
    "## Difference\n",
    "\n",
    "![Union](images/difference.png)\n",
    "\n",
    "Difference is used to find elements in \"the left\" set, but not in the \"right set\"."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "left_set = {1, 2, 3, 4}\n",
    "right_set = {3, 4, 5, 6}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "First way! \n",
    "With the `.difference()` method."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "difference_set = left_set.difference(right_set)\n",
    "print(difference_set)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The other way!\n",
    "Use the `-` character."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "difference_set = left_set - right_set\n",
    "print(difference_set)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "---\n",
    "\n",
    "## Symmetric Difference\n",
    "\n",
    "![Symmetric Difference](images/symmetric_difference.png)\n",
    "\n",
    "This is the opposite of intersection. \n",
    "Values in either the \"left set\" or the \"right set\", but not both. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "left_set = {1, 2, 3, 4}\n",
    "right_set = {3, 4, 5, 6}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "First way! \n",
    "With the `.difference()` method."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "difference_set = left_set.symmetric_difference(right_set)\n",
    "print(difference_set)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The other way!\n",
    "Use the `^` character."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "difference_set = left_set ^ right_set\n",
    "print(difference_set)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "---\n",
    "\n",
    "### YOUR TURN\n",
    "\n",
    "* Create 2 sets. \n",
    "One with all even numbers between 1 and 10, and the other as all prime numbers between 1 and 10.\n",
    "* Print out the union between the two.\n",
    "* Print the intersection.\n",
    "* Print the difference..\n",
    "* Print the symmetric difference!"
   ]
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    "### More references on Sets\n",
    "\n",
    "* [Python sets](https://docs.python.org/3.6/tutorial/datastructures.html#sets)\n",
    "* [Set intersection](https://docs.python.org/3.6/library/stdtypes.html?highlight=intersection#set.intersection)"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<hr>\n",
    "\n",
    "## Set Methods - some docs [here](https://www.w3schools.com/python/python_ref_set.asp)\n",
    "\n",
    "Just like lists, sets also have _methods_ that we can use.\n",
    "\n",
    "* `add` - Adds an element to the set\n",
    "* `clear` - Removes all elements from a set\n",
    "* `remove` - Removes a specified element from the set\n",
    "* `pop` - Removes and returns a single element from the set\n",
    "\n",
    "Plus.. \n",
    "All of the [set operations](https://docs.python.org/2/library/sets.html#set-objects) we talked about before!"
   ]
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  {
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   "source": [
    "my_set = {1, 2, 3, 4, 5}\n",
    "print(my_set)\n",
    "\n",
    "my_set.add(6)\n",
    "print('After adding ---> ', my_set)\n",
    "\n",
    "my_set.remove(6)\n",
    "print('After removing --> ', my_set)\n",
    "\n",
    "value = my_set.pop()\n",
    "print('Popped! --> ', value)\n",
    "print('Set after popped --> ', my_set)\n",
    "\n",
    "my_set.clear()\n",
    "print('All gone! --> ', my_set)"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<hr>\n",
    "\n",
    "### YOUR TURN\n",
    "\n",
    "* Create an empty set named `showroom`.\n",
    "* Add four of your favorite car model names to the set.\n",
    "* Print the length of your set.\n",
    "* Pick one of the items in your show room and add it to the set again.\n",
    "* Print your showroom. Notice how there's still only one instance of that model in there.\n",
    "* Using `update()`, add two more car models to your showroom with another set.\n",
    "* You've sold one of your cars. Remove it from the set with the `discard()` method."
   ]
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    "<hr>\n",
    "\n",
    "### YOUR TURN.. AGAIN!\n",
    "\n",
    "1. Now create another set of cars in a variable `junkyard`. Someone who owns a junkyard full of old cars has approached you about buying the entire inventory. In the new set, add some different cars, but also add a few that are the same as in the `showroom` set.\n",
    "1. Use the `intersection` method to see which cars exist in both the showroom and that junkyard.\n",
    "1. Now you're ready to buy the cars in the junkyard. Use the `union` method to combine the junkyard into your showroom.\n",
    "1. Use the `discard()` method to remove any cars that you acquired from the junkyard that you do not want in your showroom."
   ]
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