Replace sets with tuples

Author: treyhunner

part-4.ipynb

@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:c41c7b2462d1eccc5d63748331ca0f9ee5635e45f1f51c325d9a923cc48cc7ad"
+  "signature": "sha256:640caa4f1507ed924c3e826c02125468a1dc8314809695aa3b1b04bcae642559"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -514,19 +514,38 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "## Sets\n",
+      "## Tuples\n",
       "\n",
-      "Sets are unordered collections of distinct items.  Lists can have duplicates of the same item, but sets only store one copy.\n",
+      "Tuples are similar to lists except they're immutable, which means we can't change them after they've been made.\n",
       "\n",
-      "Let's say we want to make a roster of people who have RSVPed to our birthday party.  If someone RSVPs twice we don't want them to show up in our roster twice.  Let's use a set!"
+      "Tuples are comma-separated lists:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "party_roster = {\"Jessica\", \"Tom\", \"Alice\"}\n",
-      "party_roster"
+      "stuff = (1, 2, \"hello\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "stuff"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "type(stuff)"
      ],
      "language": "python",
      "metadata": {},
@@ -536,15 +555,14 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Notice how we used curly braces around our set (just like we did for dictionaries)?  What happens if we want to represent an empty set?"
+      "The parenthesis are often optional.  They're often added for clarity.  This should work too:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "empty_dictionary = {}\n",
-      "type(empty_dictionary)"
+      "stuff = 1, 2, 3"
      ],
      "language": "python",
      "metadata": {},
@@ -554,8 +572,7 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "empty_set = set()\n",
-      "type(empty_set)"
+      "stuff"
      ],
      "language": "python",
      "metadata": {},
@@ -565,14 +582,14 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Our friend Jeremy just RSVPed, let's add him to our set too:"
+      "Let's see what happens when we try to change our tuple:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "party_roster.add(\"Jeremy\")"
+      "stuff[2] = 3"
      ],
      "language": "python",
      "metadata": {},
@@ -582,24 +599,31 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "We can check for size and membership of sets and loop over them just like with sets, strings, and dictionaries."
+      "We can make an empty tuple with an empty set of parenthesis:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "\"Jessica\" in party_roster"
+      "empty = ()"
      ],
      "language": "python",
      "metadata": {},
      "outputs": []
     },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Any guesses how we can make a single-item tuple?"
+     ]
+    },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "\"Bill\" in party_roster"
+      "things = (3)"
      ],
      "language": "python",
      "metadata": {},
@@ -609,25 +633,17 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "len(party_roster)"
+      "things"
      ],
      "language": "python",
      "metadata": {},
      "outputs": []
     },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "Our party is a potluck.  Everyone is supposed to bring a dinner dish or a dessert.  Let's make sets for everyone bringing a dish and everyone bringing a dessert."
-     ]
-    },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "bringing_dish = {\"Jessica\", \"Jeremy\"}\n",
-      "bringing_dessert = {\"Alice\", \"Jeremy\"}"
+      "type(things)"
      ],
      "language": "python",
      "metadata": {},
@@ -637,17 +653,14 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Sets allow us to use set operations from math to find the union, intersection, difference, and symmetric difference between sets.  Let's try it out:"
+      "Python just sees this as a number with parenthesis around it.  The commas are the important part.  We need to add a comma after the number to make a single-item tuple:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "bringing_dish_or_dessert = bringing_dish.union(bringing_dessert)\n",
-      "bringing_dish_and_dessert = bringing_dish.intersection(bringing_dessert)\n",
-      "bringing_just_one_item = bringing_dish.symmetric_difference(bringing_dessert)\n",
-      "not_bringing_food = party_roster.difference(bringing_dish_or_dessert)"
+      "things = (3,)"
      ],
      "language": "python",
      "metadata": {},
@@ -657,10 +670,7 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "print(bringing_dish_or_dessert)\n",
-      "print(bringing_dish_and_dessert)\n",
-      "print(bringing_just_one_item)\n",
-      "print(not_bringing_food)"
+      "things"
      ],
      "language": "python",
      "metadata": {},