Updated for challenge 9
[cipher-tools.git] / enigma.ipynb
index 7c9906cbc618ee32b8dd1a5b035545263001dae8..50d708f859b6e1f2816491366da701e3b9b77592 100644 (file)
@@ -4,17 +4,71 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
+    "<a name=\"top\"></a>\n",
     "# Enigma machine\n",
-    "Specification from [Codes and Ciphers](http://www.codesandciphers.org.uk/enigma/rotorspec.htm) page.\n",
     "\n",
-    "Example Enigma machines from [Louise Dale](http://enigma.louisedade.co.uk/enigma.html) (full simulation) and [EnigmaCo](http://enigmaco.de/enigma/enigma.html) (good animation of the wheels, but no ring settings).\n",
+    "This is an implementation of an Enigma machine in Python. See below for links that describe the Enigma machine and how it was used.\n",
     "\n",
-    "There's also the nice Enigma simulator for Android by [Franklin Heath](https://franklinheath.co.uk/2012/02/04/our-first-app-published-enigma-simulator/), available on the [Google Play store](https://play.google.com/store/apps/details?id=uk.co.franklinheath.enigmasim&hl=en_GB)."
+    "The Enigma machine has a bunch of components which can be swapped or modified to change its behaviour. The components are:\n",
+    "\n",
+    "* The plugboard\n",
+    "* The wheels (three chosen from a set of five)\n",
+    "* The reflector (two available, though generally not swapped)\n",
+    "\n",
+    "The plugboard and wheel selection were changed every day. The wheel orientation was changed every message.\n",
+    "\n",
+    "## Design sketch\n",
+    "Each of the components can be thought of as a \"letter transformer\", which take a letter and input and give a different letter as output. From a given setup (plugboard setting or wheel orientation), these transformations are deterministic: if nothing moves, the same letter input will give the same letter output. Depending on the component, forward and backward transformations can be different. For instance, the wheel I converts `a` to `e` forward, and `a` to `u` backward.\n",
+    "\n",
+    "This means we can take an object oriented approach to building the Enigma machine. The machine itself is a collection (aggregation) of components. Each component keeps track of its current state. \n",
+    "\n",
+    "The components have an inheritance hierarchy.\n",
+    "\n",
+    "* [LetterTransformer](#lettertransformer)\n",
+    "  * [Plugobard](#plugboard)\n",
+    "    * [Reflector](#reflector)\n",
+    "  * [SimpleWheel](#simplewheel)\n",
+    "    * [Wheel](#wheel)\n",
+    "\n",
+    "The `LetterTransformer` is the base class and defines the basic operations all the transformers apply. \n",
+    "\n",
+    "A `Plugboard` is a type of `LetterTransformer` that swaps only some letters, and acts the same both forward and backward. The `Reflector` acts like a `Plugboard` but with 13 pairs of swaps.\n",
+    "\n",
+    "A `SimpleWheel` has different forward and backward transforms, and also rotates. A `Wheel` is the same, but the indicator \"ring\" around the outside can be rotated around the core. This ring of a `Wheel` has a notch that can control when other `SimpleWheel`s and `Wheel`s are rotated in the Enigma.\n",
+    "\n",
+    "Note that all the logic of when the wheels rotate is controlled by the Enigma machine.\n",
+    "\n",
+    "* [Engima](#enigma)\n",
+    "* [Testing Enigma](#testingenigma)\n",
+    "\n",
+    "### Implmentation note\n",
+    "The normal way to define a class in Python is to define all the methods, class variables, and instance variables at the same time. However, that makes it difficult to place the discussion of the various methods and what they do near the definitions. \n",
+    "\n",
+    "This notebook takes a variant approach of defining the base class, then defining methods in separate cells and adding them to the class with the `setattr()` procedure.\n",
+    "\n",
+    "\n",
+    "## See also\n",
+    "* Specification from [Codes and Ciphers](http://www.codesandciphers.org.uk/enigma/rotorspec.htm) page.\n",
+    "\n",
+    "* Example Enigma machines from [Louise Dale](http://enigma.louisedade.co.uk/enigma.html) (full simulation) and [EnigmaCo](http://enigmaco.de/enigma/enigma.html) (good animation of the wheels, but no ring settings).\n",
+    "\n",
+    "* There's also the nice Enigma simulator for Android by [Franklin Heath](https://franklinheath.co.uk/2012/02/04/our-first-app-published-enigma-simulator/), available on the [Google Play store](https://play.google.com/store/apps/details?id=uk.co.franklinheath.enigmasim&hl=en_GB).\n",
+    "\n",
+    "* Enigma wiring from the [Crypto Museum](http://www.cryptomuseum.com/crypto/enigma/wiring.htm)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "First, some general-purpose and utility imports. \n",
+    "\n",
+    "`pos` and `unpos` convert between letters and numbers (in range 0-25 inclusive)."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 733,
+   "execution_count": 108,
    "metadata": {
     "collapsed": true
    },
     "def unpos(number): return chr(number % 26 + ord('a'))"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The wheel specifications show what positions `a` to `z` (ignoring the ring) go to. For instance, Wheel 1 converts `a` to `e` forward, and `a` to `u` backward. The notch positions show where the wheel advance notches are on the wheel rings. The reflector specifications show the reflected pairs."
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 734,
+   "execution_count": 109,
    "metadata": {
     "collapsed": true
    },
     "beta_wheel_spec = 'leyjvcnixwpbqmdrtakzgfuhos'\n",
     "gamma_wheel_spec = 'fsokanuerhmbtiycwlqpzxvgjd'\n",
     "\n",
-    "wheel_i_pegs = ['q']\n",
-    "wheel_ii_pegs = ['e']\n",
-    "wheel_iii_pegs = ['v']\n",
-    "wheel_iv_pegs = ['j']\n",
-    "wheel_v_pegs = ['z']\n",
-    "wheel_vi_pegs = ['z', 'm']\n",
-    "wheel_vii_pegs = ['z', 'm']\n",
-    "wheel_viii_pegs = ['z', 'm']\n",
+    "wheel_i_notches = ['q']\n",
+    "wheel_ii_notches = ['e']\n",
+    "wheel_iii_notches = ['v']\n",
+    "wheel_iv_notches = ['j']\n",
+    "wheel_v_notches = ['z']\n",
+    "wheel_vi_notches = ['z', 'm']\n",
+    "wheel_vii_notches = ['z', 'm']\n",
+    "wheel_viii_notches = ['z', 'm']\n",
     "\n",
     "reflector_b_spec = 'ay br cu dh eq fs gl ip jx kn mo tz vw'\n",
     "reflector_c_spec = 'af bv cp dj ei go hy kr lz mx nw tq su'"
   },
   {
    "cell_type": "code",
-   "execution_count": 735,
+   "execution_count": 110,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "# class LetterTransformer(object):\n",
+    "#     def __init__(self, specification, raw_transform=False):\n",
+    "#         if raw_transform:\n",
+    "#             transform = specification\n",
+    "#         else:\n",
+    "#             transform = self.parse_specification(specification)\n",
+    "#         self.validate_transform(transform)\n",
+    "#         self.make_transform_map(transform)\n",
+    "    \n",
+    "#     def parse_specification(self, specification):\n",
+    "#         return list(zip(string.ascii_lowercase, clean(specification)))\n",
+    "#         # return specification\n",
+    "    \n",
+    "#     def validate_transform(self, transform):\n",
+    "#         \"\"\"A set of pairs, of from-to\"\"\"\n",
+    "#         if len(transform) != 26:\n",
+    "#             raise ValueError(\"Transform specification has {} pairs, requires 26\".\n",
+    "#                 format(len(transform)))\n",
+    "#         for p in transform:\n",
+    "#             if len(p) != 2:\n",
+    "#                 raise ValueError(\"Not all mappings in transform \"\n",
+    "#                     \"have two elements\")\n",
+    "#         if len(set([p[0] for p in transform])) != 26:\n",
+    "#             raise ValueError(\"Transform specification must list 26 origin letters\") \n",
+    "#         if len(set([p[1] for p in transform])) != 26:\n",
+    "#             raise ValueError(\"Transform specification must list 26 destination letters\") \n",
+    "\n",
+    "#     def make_empty_transform(self):\n",
+    "#         self.forward_map = [0] * 26\n",
+    "#         self.backward_map = [0] * 26\n",
+    "            \n",
+    "#     def make_transform_map(self, transform):\n",
+    "#         self.make_empty_transform()\n",
+    "#         for p in transform:\n",
+    "#             self.forward_map[pos(p[0])] = pos(p[1])\n",
+    "#             self.backward_map[pos(p[1])] = pos(p[0])\n",
+    "#         return self.forward_map, self.backward_map\n",
+    "    \n",
+    "#     def forward(self, letter):\n",
+    "#         if letter in string.ascii_lowercase:\n",
+    "#             return unpos(self.forward_map[pos(letter)])\n",
+    "#         else:\n",
+    "#             return ''\n",
+    "                \n",
+    "#     def backward(self, letter):\n",
+    "#         if letter in string.ascii_lowercase:\n",
+    "#             return unpos(self.backward_map[pos(letter)])\n",
+    "#         else:\n",
+    "#             return ''"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<a name=\"lettertransformer\"></a>\n",
+    "# Letter transformer\n",
+    "[Top](#top)\n",
+    "\n",
+    "A generic transformer of letters. All components in the Enigma are based on this. \n",
+    "\n",
+    "The transformer has two directions, `forward` and `backward`. In each direction, a given letter is transformed into a different letter. Both transformations are general permutations of the alphabet (i.e. each letter goes to one and only one new letter). There is no general requirement for the `forward` and `backward` transformations to have any particular relationship to each other (even though most do in the Enigma machine).\n",
+    "\n",
+    "When created, it must be given the transformation which should be applied. A raw transform is a sequence of letter pairs, such that `p[0]` is transformed to `p[1]` forwards, and `p[1]` goes to `p[0]` backwards.\n",
+    "\n",
+    "If the transform is not raw, it's assumed that the specification is a sequence of the `p[1]`s, and the standard alphabet gives the `p[0]`s."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 111,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
     "        else:\n",
     "            transform = self.parse_specification(specification)\n",
     "        self.validate_transform(transform)\n",
-    "        self.make_transform_map(transform)\n",
-    "    \n",
-    "    def parse_specification(self, specification):\n",
-    "        return list(zip(string.ascii_lowercase, clean(specification)))\n",
-    "        # return specification\n",
-    "    \n",
-    "    def validate_transform(self, transform):\n",
-    "        \"\"\"A set of pairs, of from-to\"\"\"\n",
-    "        if len(transform) != 26:\n",
-    "            raise ValueError(\"Transform specification has {} pairs, requires 26\".\n",
-    "                format(len(transform)))\n",
-    "        for p in transform:\n",
-    "            if len(p) != 2:\n",
-    "                raise ValueError(\"Not all mappings in transform \"\n",
-    "                    \"have two elements\")\n",
-    "        if len(set([p[0] for p in transform])) != 26:\n",
-    "            raise ValueError(\"Transform specification must list 26 origin letters\") \n",
-    "        if len(set([p[1] for p in transform])) != 26:\n",
-    "            raise ValueError(\"Transform specification must list 26 destination letters\") \n",
-    "\n",
-    "    def make_empty_transform(self):\n",
-    "        self.forward_map = [0] * 26\n",
-    "        self.backward_map = [0] * 26\n",
-    "            \n",
-    "    def make_transform_map(self, transform):\n",
-    "        self.make_empty_transform()\n",
-    "        for p in transform:\n",
-    "            self.forward_map[pos(p[0])] = pos(p[1])\n",
-    "            self.backward_map[pos(p[1])] = pos(p[0])\n",
-    "        return self.forward_map, self.backward_map\n",
-    "    \n",
-    "    def forward(self, letter):\n",
-    "        if letter in string.ascii_lowercase:\n",
-    "            return unpos(self.forward_map[pos(letter)])\n",
-    "        else:\n",
-    "            return ''\n",
-    "                \n",
-    "    def backward(self, letter):\n",
-    "        if letter in string.ascii_lowercase:\n",
-    "            return unpos(self.backward_map[pos(letter)])\n",
-    "        else:\n",
-    "            return ''"
+    "        self.make_transform_map(transform)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Parse a specification: convert a string of destination letters into a list of pairs. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 112,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def parse_specification(self, specification):\n",
+    "    return list(zip(string.ascii_lowercase, clean(specification)))\n",
+    "    # return specification\n",
+    "\n",
+    "setattr(LetterTransformer, \"parse_specification\", parse_specification)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 113,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[('a', 'e'),\n",
+       " ('b', 'k'),\n",
+       " ('c', 'm'),\n",
+       " ('d', 'f'),\n",
+       " ('e', 'l'),\n",
+       " ('f', 'g'),\n",
+       " ('g', 'd'),\n",
+       " ('h', 'q'),\n",
+       " ('i', 'v'),\n",
+       " ('j', 'z'),\n",
+       " ('k', 'n'),\n",
+       " ('l', 't'),\n",
+       " ('m', 'o'),\n",
+       " ('n', 'w'),\n",
+       " ('o', 'y'),\n",
+       " ('p', 'h'),\n",
+       " ('q', 'x'),\n",
+       " ('r', 'u'),\n",
+       " ('s', 's'),\n",
+       " ('t', 'p'),\n",
+       " ('u', 'a'),\n",
+       " ('v', 'i'),\n",
+       " ('w', 'b'),\n",
+       " ('x', 'r'),\n",
+       " ('y', 'c'),\n",
+       " ('z', 'j')]"
+      ]
+     },
+     "execution_count": 113,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "parse_specification(None, wheel_i_spec)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Checks that a transform is valid."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 114,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def validate_transform(self, transform):\n",
+    "    \"\"\"A set of pairs, of from-to\"\"\"\n",
+    "    if len(transform) != 26:\n",
+    "        raise ValueError(\"Transform specification has {} pairs, requires 26\".\n",
+    "            format(len(transform)))\n",
+    "    for p in transform:\n",
+    "        if len(p) != 2:\n",
+    "            raise ValueError(\"Not all mappings in transform \"\n",
+    "                \"have two elements\")\n",
+    "    if len(set([p[0] for p in transform])) != 26:\n",
+    "        raise ValueError(\"Transform specification must list 26 origin letters\") \n",
+    "    if len(set([p[1] for p in transform])) != 26:\n",
+    "        raise ValueError(\"Transform specification must list 26 destination letters\") \n",
+    "\n",
+    "setattr(LetterTransformer, \"validate_transform\", validate_transform)        "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The empty transform maps each letter to itself, forward and backward. A useful starting point for creating the maps needed.\n",
+    "\n",
+    "The forward and backward maps are `list`s of numbers (rather than `dict`s of letters to letters) to make the calculations easier when it comes to the wheels, and wheels with turnable indicator rings."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 115,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "# def make_empty_transform(self):\n",
+    "#     self.forward_map = [0] * 26\n",
+    "#     self.backward_map = [0] * 26\n",
+    "\n",
+    "# setattr(LetterTransformer, \"make_empty_transform\", make_empty_transform)    "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 116,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def make_empty_transform(self):\n",
+    "    self.forward_map = list(range(26))\n",
+    "    self.backward_map = list(range(26))\n",
+    "\n",
+    "setattr(LetterTransformer, \"make_empty_transform\", make_empty_transform)    "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Make the transform. Starting from an empty transform, mutate it to include the swaps. Note that the forward and backward swaps are stored separately. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 117,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def make_transform_map(self, transform):\n",
+    "    self.make_empty_transform()\n",
+    "    for p in transform:\n",
+    "        self.forward_map[pos(p[0])] = pos(p[1])\n",
+    "        self.backward_map[pos(p[1])] = pos(p[0])\n",
+    "    return self.forward_map, self.backward_map\n",
+    "\n",
+    "setattr(LetterTransformer, \"make_transform_map\", make_transform_map)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 736,
+   "execution_count": 118,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
+   "outputs": [],
+   "source": [
+    "def forward(self, letter):\n",
+    "    if letter in string.ascii_lowercase:\n",
+    "        return unpos(self.forward_map[pos(letter)])\n",
+    "    else:\n",
+    "        return ''\n",
+    "\n",
+    "def backward(self, letter):\n",
+    "    if letter in string.ascii_lowercase:\n",
+    "        return unpos(self.backward_map[pos(letter)])\n",
+    "    else:\n",
+    "        return ''\n",
+    "\n",
+    "setattr(LetterTransformer, \"forward\", forward)\n",
+    "setattr(LetterTransformer, \"backward\", backward)    "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 119,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        " ('y', 'z')]"
       ]
      },
-     "execution_count": 736,
+     "execution_count": 119,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 737,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 120,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'zyxwcabdefghijklmnopqrstuv'"
       ]
      },
-     "execution_count": 737,
+     "execution_count": 120,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 738,
+   "execution_count": 121,
    "metadata": {
-    "collapsed": false,
+    "collapsed": true,
     "scrolled": true
    },
    "outputs": [],
   },
   {
    "cell_type": "code",
-   "execution_count": 739,
+   "execution_count": 122,
    "metadata": {
-    "collapsed": false,
     "scrolled": true
    },
    "outputs": [
        "  24])"
       ]
      },
-     "execution_count": 739,
+     "execution_count": 122,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 740,
+   "execution_count": 123,
    "metadata": {
-    "collapsed": false,
     "scrolled": true
    },
    "outputs": [
        "  0])"
       ]
      },
-     "execution_count": 740,
+     "execution_count": 123,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 741,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 124,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'zyxwcabdefghijklmnopqrstuv'"
       ]
      },
-     "execution_count": 741,
+     "execution_count": 124,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 742,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 125,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'fgehijklmnopqrstuvwxyzdcba'"
       ]
      },
-     "execution_count": 742,
+     "execution_count": 125,
      "metadata": {},
      "output_type": "execute_result"
     }
     "cat(lt.backward(l) for l in string.ascii_lowercase)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<a name=\"plugboard\"></a>\n",
+    "## Plugboard\n",
+    "[Top](#top)\n",
+    "\n",
+    "A `Plugboard` is a `LetterTransformer` that swaps some pairs of letters, and does the same swaps forward and backward."
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 743,
+   "execution_count": 126,
    "metadata": {
     "collapsed": true
    },
     "                raise ValueError(\"Not all mappings in transform\"\n",
     "                    \"have two elements\")\n",
     "    \n",
-    "    def make_empty_transform(self):\n",
-    "        self.forward_map = list(range(26))\n",
-    "        self.backward_map = list(range(26))\n",
+    "    def make_empty_transform(self):\n",
+    "        self.forward_map = list(range(26))\n",
+    "        self.backward_map = list(range(26))\n",
     "        \n",
     "    def make_transform_map(self, transform):\n",
     "        expanded_transform = transform + [tuple(reversed(p)) for p in transform]\n",
   },
   {
    "cell_type": "code",
-   "execution_count": 744,
+   "execution_count": 127,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
   },
   {
    "cell_type": "code",
-   "execution_count": 745,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 128,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'zycdefghijklmnopqrstuvwxba'"
       ]
      },
-     "execution_count": 745,
+     "execution_count": 128,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 746,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 129,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'zycdefghijklmnopqrstuvwxba'"
       ]
      },
-     "execution_count": 746,
+     "execution_count": 129,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 747,
+   "execution_count": 130,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
   },
   {
    "cell_type": "code",
-   "execution_count": 748,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 131,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "('zycdefghijklmnopqrstuvwxba', 'zycdefghijklmnopqrstuvwxba')"
       ]
      },
-     "execution_count": 748,
+     "execution_count": 131,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 749,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 132,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "('ugcdypblnzkhmisfrqoxavwtej', 'ugcdypblnzkhmisfrqoxavwtej')"
       ]
      },
-     "execution_count": 749,
+     "execution_count": 132,
      "metadata": {},
      "output_type": "execute_result"
     }
     "cat(pb.forward(l) for l in string.ascii_lowercase), cat(pb.backward(l) for l in string.ascii_lowercase)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<a name=\"reflector\"></a>\n",
+    "## Reflector\n",
+    "[Top](#top)\n",
+    "\n",
+    "A `Reflector` is a `Plugboard` that takes exactly 13 pairs of letters to swap."
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 750,
+   "execution_count": 133,
    "metadata": {
     "collapsed": true
    },
   },
   {
    "cell_type": "code",
-   "execution_count": 751,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 134,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        " ('v', 'w')]"
       ]
      },
-     "execution_count": 751,
+     "execution_count": 134,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 752,
+   "execution_count": 135,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
   },
   {
    "cell_type": "code",
-   "execution_count": 753,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 136,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'yruhqsldpxngokmiebfzcwvjat'"
       ]
      },
-     "execution_count": 753,
+     "execution_count": 136,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 754,
+   "execution_count": 137,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
   },
   {
    "cell_type": "code",
-   "execution_count": 755,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 138,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'fvpjiaoyedrzxwgctkuqsbnmhl'"
       ]
      },
-     "execution_count": 755,
+     "execution_count": 138,
      "metadata": {},
      "output_type": "execute_result"
     }
    ]
   },
   {
-   "cell_type": "code",
-   "execution_count": 756,
-   "metadata": {
-    "collapsed": true
-   },
-   "outputs": [],
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<a name=\"simplewheel\"></a>\n",
+    "## SimpleWheel\n",
+    "[Top](#top)\n",
+    "\n",
+    "A `SimpleWheel` has different forward and backward maps, and also a position. The position is set with the `set_position` method (and initially in the creator), and the wheel can advance using the `advance` method. \n",
+    "\n",
+    "How the position is used is best explained with an example. The Enigma wheel 1, in the neutral position, transforms `a` to `e` (+4 letters) and `b` to `k` (+10 letters). When the wheel is in position `b` and an `a` in enciphered, it's the _second_ element of the map that's used, so `a` would be advanced 10 letters, to give `j`.\n",
+    "\n",
+    "This means that when using the letter transformation maps, you use the element in the map that's offset by the position of the wheel. When enciphering a `c`, you'd normally use transformation at position 2 in the map; if the wheel is in position 7, you'd instead use the transform at position 2 + 7 = 9 in the map.\n",
+    "\n",
+    "There are various modulus operators to keep the numbers in the requried range, meaning you can wrap around the map and around the wheel.\n",
+    "\n",
+    "Note the use of `__getattribute__` to give a more human-friendly version of the position without making it a method call. That allows you to write `wheel.position` and `wheel.position_l` and get the appropriate answers."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 139,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
    "source": [
     "class SimpleWheel(LetterTransformer):\n",
     "    def __init__(self, transform, position='a', raw_transform=False):\n",
     "        super(SimpleWheel, self).__init__(transform, raw_transform)\n",
     "        self.set_position(position)\n",
     "        \n",
-    "    def __getattribute__(self,name):\n",
+    "    def __getattribute__(self, name):\n",
     "        if name=='position_l':\n",
     "            return unpos(self.position)\n",
     "        else:\n",
-    "            return object.__getattribute__(self, name)\n",
-    "    \n",
-    "    def set_position(self, position):\n",
-    "        self.position = ord(position) - ord('a')\n",
-    "    \n",
-    "    def forward(self, letter):\n",
-    "        if letter in string.ascii_lowercase:\n",
-    "            return unpos((self.forward_map[(pos(letter) + self.position) % 26] - self.position))\n",
-    "        else:\n",
-    "            return ''\n",
-    "                \n",
-    "    def backward(self, letter):\n",
-    "        if letter in string.ascii_lowercase:\n",
-    "            return unpos((self.backward_map[(pos(letter) + self.position) % 26] - self.position))\n",
-    "        else:\n",
-    "            return ''\n",
+    "            return object.__getattribute__(self, name)  "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Set the wheel to a new position. Note that it expects a letter, not a number."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 140,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def set_position(self, position):\n",
+    "    self.position = ord(position) - ord('a')\n",
+    "        \n",
+    "setattr(SimpleWheel, 'set_position', set_position)       "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Advance the wheel one step. Note that advancing beyond position 25 moves back to 0."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 141,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def advance(self):\n",
+    "    self.position = (self.position + 1) % 26\n",
+    "    return self.position\n",
+    "\n",
+    "setattr(SimpleWheel, 'advance', advance)    "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Do the encipherment forward and backward. Note how the map element to use is affected by the wheel position, and how the modulus wraps that map element around the wheel if needed."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 142,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def forward(self, letter):\n",
+    "    if letter in string.ascii_lowercase:\n",
+    "        return unpos((self.forward_map[(pos(letter) + self.position) % 26] - self.position))\n",
+    "    else:\n",
+    "        return ''\n",
+    "\n",
+    "def backward(self, letter):\n",
+    "    if letter in string.ascii_lowercase:\n",
+    "        return unpos((self.backward_map[(pos(letter) + self.position) % 26] - self.position))\n",
+    "    else:\n",
+    "        return ''\n",
     "        \n",
-    "    def advance(self):\n",
-    "        self.position = (self.position + 1) % 26\n",
-    "        return self.position"
+    "setattr(SimpleWheel, 'forward', forward)        \n",
+    "setattr(SimpleWheel, 'backward', backward)  "
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 757,
+   "execution_count": 143,
    "metadata": {
-    "collapsed": false,
     "scrolled": true
    },
    "outputs": [
        " ('z', 'j')]"
       ]
      },
-     "execution_count": 757,
+     "execution_count": 143,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 758,
+   "execution_count": 144,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
   },
   {
    "cell_type": "code",
-   "execution_count": 759,
+   "execution_count": 145,
    "metadata": {
-    "collapsed": false
+    "scrolled": true
    },
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "('ekmflgdqvzntowyhxuspaibrcj', 'uwygadfpvzbeckmthxslrinqoj')"
+       "[4,\n",
+       " 10,\n",
+       " 12,\n",
+       " 5,\n",
+       " 11,\n",
+       " 6,\n",
+       " 3,\n",
+       " 16,\n",
+       " 21,\n",
+       " 25,\n",
+       " 13,\n",
+       " 19,\n",
+       " 14,\n",
+       " 22,\n",
+       " 24,\n",
+       " 7,\n",
+       " 23,\n",
+       " 20,\n",
+       " 18,\n",
+       " 15,\n",
+       " 0,\n",
+       " 8,\n",
+       " 1,\n",
+       " 17,\n",
+       " 2,\n",
+       " 9]"
+      ]
+     },
+     "execution_count": 145,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "wheel_1.forward_map"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 146,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'j'"
+      ]
+     },
+     "execution_count": 146,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "wheel_1.advance()\n",
+    "wheel_1.forward('a')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 147,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "('jlekfcpuymsnvxgwtrozhaqbid', 'vxfzceouyadbjlsgwrkqhmpnit')"
       ]
      },
-     "execution_count": 759,
+     "execution_count": 147,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 760,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 148,
+   "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "'a'"
+       "'b'"
       ]
      },
-     "execution_count": 760,
+     "execution_count": 148,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 761,
+   "execution_count": 149,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
   },
   {
    "cell_type": "code",
-   "execution_count": 762,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 150,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "('ajdksiruxblhwtmcqgznpyfvoe', 'ajpczwrlfbdkotyuqgenhxmivs')"
       ]
      },
-     "execution_count": 762,
+     "execution_count": 150,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 763,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 151,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "('bdfhjlcprtxvznyeiwgakmusqo', 'tagbpcsdqeufvnzhyixjwlrkom')"
       ]
      },
-     "execution_count": 763,
+     "execution_count": 151,
      "metadata": {},
      "output_type": "execute_result"
     }
     "cat(wheel_3.forward(l) for l in string.ascii_lowercase), cat(wheel_3.backward(l) for l in string.ascii_lowercase)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<a name=\"wheel\"></a>\n",
+    "## Wheel\n",
+    "[Top](#top)\n",
+    "\n",
+    "This is the same as a `SimpleWheel`, but with the addition of a ring.\n",
+    "\n",
+    "The ring is moveable around the core of the wheel (with the wiring). This means that moving the ring changes the orientation of the core and wiring for the same setting.\n",
+    "\n",
+    "| Wheel with notch | Notch showing peg to hold it in place |\n",
+    "| ---------------- | ------------------------------------- |\n",
+    "| <img src=\"enigma-notch.jpg\" alt=\"Enigma wheel with notch\" width=300> | <img src=\"dtu_notch_big.jpg\" alt=\"Enigma wheel with notch\" width=300> |\n",
+    "| (From [Crypto museum](http://www.cryptomuseum.com/crypto/enigma/img/300879/035/full.jpg)) | From [Matematik Sider](http://www.matematiksider.dk/enigma/dtu_notch_big.jpg) |\n",
+    "\n",
+    "Though it's not very visible in the right hand image, the extra metal below the ring shows a spring-loaded peg on the wheel core which drops into the ring, with one hole per letter. The ring setting is where the peg drops into the ring.\n",
+    "\n",
+    "The notch setting is used in the full Enigma to control when the wheels step forward.\n",
+    "\n",
+    "Note that the constructor calls the superclass's constructor, then sets the positions properly with a call to `set_position`."
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 764,
+   "execution_count": 152,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
     "class Wheel(SimpleWheel):\n",
-    "    def __init__(self, transform, ring_peg_letters, ring_setting=1, position='a', raw_transform=False):\n",
-    "        self.ring_peg_letters = ring_peg_letters\n",
+    "    def __init__(self, transform, ring_notch_letters, ring_setting=1, position='a', raw_transform=False):\n",
+    "        self.ring_notch_letters = ring_notch_letters\n",
     "        self.ring_setting = ring_setting\n",
     "        super(Wheel, self).__init__(transform, position=position, raw_transform=raw_transform)\n",
-    "        self.set_position(position)\n",
-    "        \n",
-    "    def __getattribute__(self,name):\n",
-    "        if name=='position_l':\n",
-    "            return unpos(self.position + self.ring_setting - 1)\n",
-    "        else:\n",
-    "            return object.__getattribute__(self, name)\n",
+    "        self.set_position(position)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The `position` of the wheel is the orientation of the core. It's the same as the ring if the ring setting is 1. The `position_l` attribute is used to report the position of the ring letter, which is what the Enigma operator would see. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 153,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def __getattribute__(self,name):\n",
+    "    if name=='position_l':\n",
+    "        return unpos(self.position + self.ring_setting - 1)\n",
+    "    else:\n",
+    "        return object.__getattribute__(self, name)\n",
     "\n",
-    "    def set_position(self, position):\n",
+    "def set_position(self, position):\n",
+    "#     self.position = (pos(position) - self.ring_setting + 1) % 26\n",
+    "    if isinstance(position, str):\n",
     "        self.position = (pos(position) - self.ring_setting + 1) % 26\n",
-    "        # self.position_l = position\n",
-    "        self.peg_positions = [(pos(p) - pos(position)) % 26  for p in self.ring_peg_letters]\n",
+    "    else:\n",
+    "        self.position = (position - self.ring_setting) % 26\n",
+    "#     self.notch_positions = [(pos(position) - pos(p)) % 26  for p in self.ring_notch_letters]\n",
+    "    self.notch_positions = [(self.position + self.ring_setting - 1 - pos(p)) % 26  for p in self.ring_notch_letters]\n",
     "        \n",
-    "    def advance(self):\n",
-    "        super(Wheel, self).advance()\n",
-    "        self.peg_positions = [(p - 1) % 26 for p in self.peg_positions]\n",
-    "        # self.position_l = unpos(self.position + self.ring_setting - 1)\n",
-    "        return self.position"
+    "setattr(Wheel, '__getattribute__', __getattribute__)        \n",
+    "setattr(Wheel, 'set_position', set_position)    "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Advance the wheel. Again, note the superclass call, followed by the update of the notch positions."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 765,
+   "execution_count": 154,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
-    "wheel_3 = Wheel(wheel_iii_spec, wheel_iii_pegs, position='b', ring_setting=1)"
+    "def advance(self):\n",
+    "        super(Wheel, self).advance()\n",
+    "        self.notch_positions = [(p + 1) % 26 for p in self.notch_positions]\n",
+    "        # self.position_l = unpos(self.position + self.ring_setting - 1)\n",
+    "        return self.position\n",
+    "    \n",
+    "setattr(Wheel, 'advance', advance)    "
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 766,
+   "execution_count": 155,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
+   "outputs": [],
+   "source": [
+    "wheel_3 = Wheel(wheel_iii_spec, wheel_iii_notches, position='b', ring_setting=1)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 156,
+   "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "(1, [20])"
+       "(1, [6])"
       ]
      },
-     "execution_count": 766,
+     "execution_count": 156,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "wheel_3.position, wheel_3.peg_positions"
+    "wheel_3.position, wheel_3.notch_positions"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 767,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 157,
+   "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "(25, [24, 11])"
+       "(25, [2, 15])"
       ]
      },
-     "execution_count": 767,
+     "execution_count": 157,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "wheel_6 = Wheel(wheel_vi_spec, wheel_vi_pegs, position='b', ring_setting=3)\n",
-    "wheel_6.position, wheel_6.peg_positions"
+    "wheel_6 = Wheel(wheel_vi_spec, wheel_vi_notches, position='b', ring_setting=3)\n",
+    "wheel_6.position, wheel_6.notch_positions"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 768,
+   "execution_count": 158,
    "metadata": {
-    "collapsed": false,
     "scrolled": true
    },
    "outputs": [
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "0 [23, 10]\n",
-      "1 [22, 9]\n",
-      "2 [21, 8]\n",
-      "3 [20, 7]\n",
-      "4 [19, 6]\n",
-      "5 [18, 5]\n",
-      "6 [17, 4]\n",
-      "7 [16, 3]\n",
-      "8 [15, 2]\n",
-      "9 [14, 1]\n",
+      "0 [3, 16]\n",
+      "1 [4, 17]\n",
+      "2 [5, 18]\n",
+      "3 [6, 19]\n",
+      "4 [7, 20]\n",
+      "5 [8, 21]\n",
+      "6 [9, 22]\n",
+      "7 [10, 23]\n",
+      "8 [11, 24]\n",
+      "9 [12, 25]\n",
       "10 [13, 0]\n",
-      "11 [12, 25]\n",
-      "12 [11, 24]\n",
-      "13 [10, 23]\n",
-      "14 [9, 22]\n",
-      "15 [8, 21]\n",
-      "16 [7, 20]\n",
-      "17 [6, 19]\n",
-      "18 [5, 18]\n",
-      "19 [4, 17]\n",
-      "20 [3, 16]\n",
-      "21 [2, 15]\n",
-      "22 [1, 14]\n",
+      "11 [14, 1]\n",
+      "12 [15, 2]\n",
+      "13 [16, 3]\n",
+      "14 [17, 4]\n",
+      "15 [18, 5]\n",
+      "16 [19, 6]\n",
+      "17 [20, 7]\n",
+      "18 [21, 8]\n",
+      "19 [22, 9]\n",
+      "20 [23, 10]\n",
+      "21 [24, 11]\n",
+      "22 [25, 12]\n",
       "23 [0, 13]\n",
-      "24 [25, 12]\n",
-      "25 [24, 11]\n",
-      "0 [23, 10]\n"
+      "24 [1, 14]\n",
+      "25 [2, 15]\n",
+      "0 [3, 16]\n"
      ]
     }
    ],
    "source": [
     "for _ in range(27):\n",
     "    wheel_6.advance()\n",
-    "    print(wheel_6.position, wheel_6.peg_positions)"
+    "    print(wheel_6.position, wheel_6.notch_positions)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 159,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "wheel = Wheel(wheel_iii_spec, wheel_iii_notches, position='b', \n",
+    "            ring_setting=3)\n",
+    "wheel.set_position(12)\n",
+    "assert(wheel.position == 9)\n",
+    "assert(16 in wheel.notch_positions)\n",
+    "assert(wheel.position_l =='l')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 160,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[16]"
+      ]
+     },
+     "execution_count": 160,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "wheel.notch_positions"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 161,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'l'"
+      ]
+     },
+     "execution_count": 161,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "wheel.position_l"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 769,
+   "execution_count": 162,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
-    "wheel_3 = Wheel(wheel_iii_spec, wheel_iii_pegs, position='b', ring_setting=1)\n",
+    "wheel_3 = Wheel(wheel_iii_spec, wheel_iii_notches, position='b', ring_setting=1)\n",
     "assert(wheel_3.position == 1)\n",
-    "assert(wheel_3.peg_positions == [20])\n",
+    "assert(wheel_3.notch_positions == [6])\n",
     "assert(wheel_3.position_l == 'b')\n",
     "wheel_3.advance()\n",
     "assert(wheel_3.position == 2)\n",
-    "assert(wheel_3.peg_positions == [19])\n",
+    "assert(wheel_3.notch_positions == [7])\n",
     "assert(wheel_3.position_l == 'c')"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 770,
+   "execution_count": 163,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[2, 15]"
+      ]
+     },
+     "execution_count": 163,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "wheel_6 = Wheel(wheel_vi_spec, wheel_vi_notches, position='b', ring_setting=3)\n",
+    "wheel_6.notch_positions"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 164,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
-    "wheel_6 = Wheel(wheel_vi_spec, wheel_vi_pegs, position='b', ring_setting=3)\n",
+    "wheel_6 = Wheel(wheel_vi_spec, wheel_vi_notches, position='b', ring_setting=3)\n",
     "assert(cat(wheel_6.forward(l) for l in string.ascii_lowercase) == 'xkqhwpvngzrcfoiaselbtymjdu')\n",
     "assert(cat(wheel_6.backward(l) for l in string.ascii_lowercase) == 'ptlyrmidoxbswhnfckquzgeavj')\n",
     "assert(wheel_6.position == 25)\n",
-    "assert(11 in wheel_6.peg_positions)\n",
-    "assert(24 in wheel_6.peg_positions)\n",
+    "assert(2 in wheel_6.notch_positions)\n",
+    "assert(15 in wheel_6.notch_positions)\n",
     "assert(wheel_6.position_l == 'b')\n",
     "\n",
     "wheel_6.advance()\n",
     "assert(cat(wheel_6.forward(l) for l in string.ascii_lowercase) == 'jpgvoumfyqbenhzrdkasxlictw')\n",
     "assert(cat(wheel_6.backward(l) for l in string.ascii_lowercase) == 'skxqlhcnwarvgmebjptyfdzuio')\n",
     "assert(wheel_6.position == 0)\n",
-    "assert(10 in wheel_6.peg_positions)\n",
-    "assert(23 in wheel_6.peg_positions)\n",
+    "assert(3 in wheel_6.notch_positions)\n",
+    "assert(16 in wheel_6.notch_positions)\n",
     "assert(wheel_6.position_l == 'c')\n",
     "\n",
     "for _ in range(22): wheel_6.advance()\n",
     "assert(cat(wheel_6.forward(l) for l in string.ascii_lowercase) == 'mgxantkzsyqjcufirldvhoewbp')\n",
     "assert(cat(wheel_6.backward(l) for l in string.ascii_lowercase) == 'dymswobuplgraevzkqifntxcjh')\n",
     "assert(wheel_6.position == 22)\n",
-    "assert(1 in wheel_6.peg_positions)\n",
-    "assert(14 in wheel_6.peg_positions)\n",
+    "assert(25 in wheel_6.notch_positions)\n",
+    "assert(12 in wheel_6.notch_positions)\n",
     "assert(wheel_6.position_l == 'y')\n",
     "\n",
     "wheel_6.advance()\n",
     "assert(cat(wheel_6.forward(l) for l in string.ascii_lowercase) == 'fwzmsjyrxpibtehqkcugndvaol')\n",
     "assert(cat(wheel_6.backward(l) for l in string.ascii_lowercase) == 'xlrvnatokfqzduyjphemswbigc')\n",
     "assert(wheel_6.position == 23)\n",
-    "assert(0 in wheel_6.peg_positions)\n",
-    "assert(13 in wheel_6.peg_positions)\n",
+    "assert(0 in wheel_6.notch_positions)\n",
+    "assert(13 in wheel_6.notch_positions)\n",
     "assert(wheel_6.position_l == 'z')\n",
     "\n",
     "wheel_6.advance()\n",
     "assert(cat(wheel_6.forward(l) for l in string.ascii_lowercase) == 'vylrixqwohasdgpjbtfmcuznke')\n",
     "assert(cat(wheel_6.backward(l) for l in string.ascii_lowercase) == 'kqumzsnjepyctxiogdlrvahfbw')\n",
     "assert(wheel_6.position == 24)\n",
-    "assert(25 in wheel_6.peg_positions)\n",
-    "assert(12 in wheel_6.peg_positions)\n",
+    "assert(1 in wheel_6.notch_positions)\n",
+    "assert(14 in wheel_6.notch_positions)\n",
     "assert(wheel_6.position_l == 'a')\n",
     "\n",
     "wheel_6.advance()\n",
     "assert(cat(wheel_6.forward(l) for l in string.ascii_lowercase) == 'xkqhwpvngzrcfoiaselbtymjdu')\n",
     "assert(cat(wheel_6.backward(l) for l in string.ascii_lowercase) == 'ptlyrmidoxbswhnfckquzgeavj')\n",
     "assert(wheel_6.position == 25)\n",
-    "assert(24 in wheel_6.peg_positions)\n",
-    "assert(11 in wheel_6.peg_positions)\n",
+    "assert(2 in wheel_6.notch_positions)\n",
+    "assert(15 in wheel_6.notch_positions)\n",
     "assert(wheel_6.position_l == 'b')\n",
     "\n",
     "wheel_6.advance()\n",
     "assert(cat(wheel_6.forward(l) for l in string.ascii_lowercase) == 'jpgvoumfyqbenhzrdkasxlictw')\n",
     "assert(cat(wheel_6.backward(l) for l in string.ascii_lowercase) == 'skxqlhcnwarvgmebjptyfdzuio')\n",
     "assert(wheel_6.position == 0)\n",
-    "assert(23 in wheel_6.peg_positions)\n",
-    "assert(10 in wheel_6.peg_positions)\n",
+    "assert(3 in wheel_6.notch_positions)\n",
+    "assert(16 in wheel_6.notch_positions)\n",
     "assert(wheel_6.position_l == 'c')"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 771,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 165,
+   "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "(0, 'c', [23, 10])"
+       "(0, 'c', [3, 16])"
       ]
      },
-     "execution_count": 771,
+     "execution_count": 165,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "wheel_6.position, wheel_6.position_l, wheel_6.peg_positions"
+    "wheel_6.position, wheel_6.position_l, wheel_6.notch_positions"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<a name=\"enigma\"></a>\n",
+    "## Enigma\n",
+    "[Top](#top)\n",
+    "\n",
+    "This is the full Enigma machine.\n",
+    "\n",
+    "It's a collection of the various components defined above. There are three wheels (left, middle, and right), a plugboard, and a reflector.\n",
+    "\n",
+    "The `__getattribute__` method returns the state of the machine in friendly form, generally by asking the components to return the relevant attributes."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 772,
-   "metadata": {
-    "collapsed": true
-   },
+   "execution_count": 167,
+   "metadata": {},
    "outputs": [],
    "source": [
     "class Enigma(object):\n",
     "    def __init__(self, reflector_spec,\n",
-    "                 left_wheel_spec, left_wheel_pegs,\n",
-    "                 middle_wheel_spec, middle_wheel_pegs,\n",
-    "                 right_wheel_spec, right_wheel_pegs,\n",
+    "                 left_wheel_spec, left_wheel_notches,\n",
+    "                 middle_wheel_spec, middle_wheel_notches,\n",
+    "                 right_wheel_spec, right_wheel_notches,\n",
     "                 left_ring_setting, middle_ring_setting, right_ring_setting,\n",
     "                 plugboard_setting):\n",
     "        self.reflector = Reflector(reflector_spec)\n",
-    "        self.left_wheel = Wheel(left_wheel_spec, left_wheel_pegs, ring_setting=left_ring_setting)\n",
-    "        self.middle_wheel = Wheel(middle_wheel_spec, middle_wheel_pegs, ring_setting=middle_ring_setting)\n",
-    "        self.right_wheel = Wheel(right_wheel_spec, right_wheel_pegs, ring_setting=right_ring_setting)\n",
+    "        self.left_wheel = Wheel(left_wheel_spec, left_wheel_notches, ring_setting=left_ring_setting)\n",
+    "        self.middle_wheel = Wheel(middle_wheel_spec, middle_wheel_notches, ring_setting=middle_ring_setting)\n",
+    "        self.right_wheel = Wheel(right_wheel_spec, right_wheel_notches, ring_setting=right_ring_setting)\n",
     "        self.plugboard = Plugboard(plugboard_setting)\n",
     "        \n",
     "    def __getattribute__(self,name):\n",
     "            return self.left_wheel.position, self.middle_wheel.position, self.right_wheel.position \n",
     "        elif name=='wheel_positions_l':\n",
     "            return self.left_wheel.position_l, self.middle_wheel.position_l, self.right_wheel.position_l \n",
-    "        elif name=='peg_positions':\n",
-    "            return self.left_wheel.peg_positions, self.middle_wheel.peg_positions, self.right_wheel.peg_positions\n",
+    "        elif name=='notch_positions':\n",
+    "            return (self.left_wheel.notch_positions, \n",
+    "                    self.middle_wheel.notch_positions, \n",
+    "                    self.right_wheel.notch_positions)\n",
     "        else:\n",
-    "            return object.__getattribute__(self, name)\n",
-    "\n",
-    "    \n",
-    "    def set_wheels(self, left_wheel_position, middle_wheel_position, right_wheel_position):\n",
-    "        self.left_wheel.set_position(left_wheel_position)\n",
-    "        self.middle_wheel.set_position(middle_wheel_position)\n",
-    "        self.right_wheel.set_position(right_wheel_position)\n",
-    "        \n",
-    "    def lookup(self, letter):\n",
-    "        a = self.plugboard.forward(letter)\n",
-    "        b = self.right_wheel.forward(a)\n",
-    "        c = self.middle_wheel.forward(b)\n",
-    "        d = self.left_wheel.forward(c)\n",
-    "        e = self.reflector.forward(d)\n",
-    "        f = self.left_wheel.backward(e)\n",
-    "        g = self.middle_wheel.backward(f)\n",
-    "        h = self.right_wheel.backward(g)\n",
-    "        i = self.plugboard.backward(h)\n",
-    "        return i\n",
-    "    \n",
-    "    def advance(self):\n",
-    "        advance_middle = False\n",
-    "        advance_left = False\n",
-    "        if 0 in self.right_wheel.peg_positions:\n",
-    "            advance_middle = True\n",
-    "        if 0 in self.middle_wheel.peg_positions:\n",
-    "            advance_left = True\n",
-    "            advance_middle = True\n",
-    "        self.right_wheel.advance()\n",
-    "        if advance_middle: self.middle_wheel.advance()\n",
-    "        if advance_left: self.left_wheel.advance()\n",
-    "            \n",
-    "    def encipher_letter(self, letter):\n",
-    "        self.advance()\n",
-    "        return self.lookup(letter)\n",
-    "    \n",
-    "    def encipher(self, message):\n",
-    "        enciphered = ''\n",
-    "        for letter in clean(message):\n",
-    "            enciphered += self.encipher_letter(letter)\n",
-    "        return enciphered"
+    "            return object.__getattribute__(self, name)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Set the wheels to the initial positions. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 168,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def set_wheels(self, left_wheel_position, middle_wheel_position, right_wheel_position):\n",
+    "    self.left_wheel.set_position(left_wheel_position)\n",
+    "    self.middle_wheel.set_position(middle_wheel_position)\n",
+    "    self.right_wheel.set_position(right_wheel_position)\n",
+    "\n",
+    "setattr(Enigma, 'set_wheels', set_wheels)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "`lookup` just follows a path through the machine without changing the positions of any parts. It just follows a signal from the input, thorough all the components, to the reflector, back through all the components, to the output."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 169,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def lookup(self, letter):\n",
+    "    a = self.plugboard.forward(letter)\n",
+    "    b = self.right_wheel.forward(a)\n",
+    "    c = self.middle_wheel.forward(b)\n",
+    "    d = self.left_wheel.forward(c)\n",
+    "    e = self.reflector.forward(d)\n",
+    "    f = self.left_wheel.backward(e)\n",
+    "    g = self.middle_wheel.backward(f)\n",
+    "    h = self.right_wheel.backward(g)\n",
+    "    i = self.plugboard.backward(h)\n",
+    "    return i\n",
+    "\n",
+    "setattr(Enigma, 'lookup', lookup)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "`advance` moves the wheels on one step. The right wheel always advances. If the notch is in the zero position, the wheel also advances the wheel to the left. \n",
+    "\n",
+    "It follows the 'double stepping' behaviour of the engima machines."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 170,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def advance(self):\n",
+    "    advance_middle = False\n",
+    "    advance_left = False\n",
+    "    if 0 in self.right_wheel.notch_positions:\n",
+    "        advance_middle = True\n",
+    "    if 0 in self.middle_wheel.notch_positions:\n",
+    "        advance_left = True\n",
+    "        advance_middle = True\n",
+    "    self.right_wheel.advance()\n",
+    "    if advance_middle: self.middle_wheel.advance()\n",
+    "    if advance_left: self.left_wheel.advance()\n",
+    "\n",
+    "setattr(Enigma, 'advance', advance)        "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Finally, encipher letters and messages. \n",
+    "\n",
+    "Note that the wheels advance _before_ the letter signal is sent through the machine: in the physical machine, the advancing is done by pressing the key on the keyboard. \n",
+    "\n",
+    "Also note that the messages are cleaned before use, so letters are converted to lower case and non-letters are removed."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 220,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def encipher_letter(self, letter):\n",
+    "    self.advance()\n",
+    "    return self.lookup(letter)\n",
+    "\n",
+    "def encipher(self, message, debug=False):\n",
+    "    enciphered = ''\n",
+    "    for letter in clean(message):\n",
+    "        enciphered += self.encipher_letter(letter)\n",
+    "        if debug:\n",
+    "            print('Wheels now', list(self.wheel_positions_l), 'enciphering {} -> {}'.format(letter, self.lookup(letter)))\n",
+    "    return enciphered\n",
+    "\n",
+    "setattr(Enigma, 'encipher_letter', encipher_letter)\n",
+    "setattr(Enigma, 'encipher', encipher)\n",
+    "setattr(Enigma, 'decipher', encipher)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<a name=\"testingenigma\"></a>\n",
+    "## Testing Enigma\n",
+    "[Top](#top)\n",
+    "\n",
+    "Some tests of the Enigma machine."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 773,
+   "execution_count": 172,
    "metadata": {
-    "collapsed": false
+    "collapsed": true
    },
    "outputs": [],
    "source": [
     "enigma = Enigma(reflector_b_spec, \n",
-    "                wheel_i_spec, wheel_i_pegs,\n",
-    "                wheel_ii_spec, wheel_ii_pegs,\n",
-    "                wheel_iii_spec, wheel_iii_pegs,\n",
+    "                wheel_i_spec, wheel_i_notches,\n",
+    "                wheel_ii_spec, wheel_ii_notches,\n",
+    "                wheel_iii_spec, wheel_iii_notches,\n",
     "                1, 1, 1,\n",
     "                '')"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 774,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 173,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'u'"
       ]
      },
-     "execution_count": 774,
+     "execution_count": 173,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 775,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 174,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'a'"
       ]
      },
-     "execution_count": 775,
+     "execution_count": 174,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 776,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 175,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'uejobtpzwcnsrkdgvmlfaqiyxh'"
       ]
      },
-     "execution_count": 776,
+     "execution_count": 175,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 777,
+   "execution_count": 176,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'abcdefghijklmnopqrstuvwxyz'"
+      ]
+     },
+     "execution_count": 176,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "cat(enigma.lookup(enigma.lookup(l)) for l in string.ascii_lowercase)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 177,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "assert(cat(enigma.lookup(enigma.lookup(l)) for l in string.ascii_lowercase) == string.ascii_lowercase)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 178,
    "metadata": {
-    "collapsed": false,
     "scrolled": true
    },
    "outputs": [
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "0 :: a a a ; [16] [4] [21] uejobtpzwcnsrkdgvmlfaqiyxh\n",
-      "1 :: a a b ; [16] [4] [20] baqmfexihswpdytlcvjozrkgnu\n",
-      "2 :: a a c ; [16] [4] [19] djralkwpobfeyqihncxzvugsmt\n",
-      "3 :: a a d ; [16] [4] [18] zlejcuitgdmbkonsvxphfqyrwa\n",
-      "4 :: a a e ; [16] [4] [17] gcblwtakqzhdosmxiunfryepvj\n",
-      "5 :: a a f ; [16] [4] [16] osnirgfmdpvuhcajwebxlkqtzy\n",
-      "6 :: a a g ; [16] [4] [15] wymvnqzjlhoicekuftxrpdasbg\n",
-      "7 :: a a h ; [16] [4] [14] cjafkdztpbeuormiwnvhlsqyxg\n",
-      "8 :: a a i ; [16] [4] [13] xijuyslvbczgnmqwotfrdhpaek\n",
-      "9 :: a a j ; [16] [4] [12] lfzrwbytjisaovmuxdkhpneqgc\n",
-      "10 :: a a k ; [16] [4] [11] tkezcqynuwbpvhslfxoaimjrgd\n",
-      "11 :: a a l ; [16] [4] [10] kiwfnduxbsaotelqpvjmgrchzy\n",
-      "12 :: a a m ; [16] [4] [9] sfkutbpoxycrnmhgwlaedzqijv\n",
-      "13 :: a a n ; [16] [4] [8] baqwlkhgrsfextpocijnvudmzy\n",
-      "14 :: a a o ; [16] [4] [7] teofbdzxqkjyrscvimnawpuhlg\n",
-      "15 :: a a p ; [16] [4] [6] mhypswrbzxqvaondkgeutlfjci\n",
-      "16 :: a a q ; [16] [4] [5] cpasnrhgkuixzevbyfdwjotlqm\n",
-      "17 :: a a r ; [16] [4] [4] dlfatcjwygvbnmzrxpueskhqio\n",
-      "18 :: a a s ; [16] [4] [3] lxymzjuqtfpadsrkhonigwvbce\n",
-      "19 :: a a t ; [16] [4] [2] puvioztjdhxmlyeawsrgbcqknf\n",
-      "20 :: a a u ; [16] [4] [1] baigpldqcowfyzjehvtsxrkumn\n",
-      "21 :: a a v ; [16] [4] [0] mnvfydiwgzsoablrxpkutchqej\n",
-      "22 :: a b w ; [16] [3] [25] ulfopcykswhbzvderqixanjtgm\n",
-      "23 :: a b x ; [16] [3] [24] qmwftdyovursbzhxaklejicpgn\n",
-      "24 :: a b y ; [16] [3] [23] oljmzxrvucybdqasngpwihtfke\n",
-      "25 :: a b z ; [16] [3] [22] fwevcalzxutgysrqponkjdbimh\n"
+      "0 :: a a a ; [10] [22] [5] uejobtpzwcnsrkdgvmlfaqiyxh\n",
+      "1 :: a a b ; [10] [22] [6] baqmfexihswpdytlcvjozrkgnu\n",
+      "2 :: a a c ; [10] [22] [7] djralkwpobfeyqihncxzvugsmt\n",
+      "3 :: a a d ; [10] [22] [8] zlejcuitgdmbkonsvxphfqyrwa\n",
+      "4 :: a a e ; [10] [22] [9] gcblwtakqzhdosmxiunfryepvj\n",
+      "5 :: a a f ; [10] [22] [10] osnirgfmdpvuhcajwebxlkqtzy\n",
+      "6 :: a a g ; [10] [22] [11] wymvnqzjlhoicekuftxrpdasbg\n",
+      "7 :: a a h ; [10] [22] [12] cjafkdztpbeuormiwnvhlsqyxg\n",
+      "8 :: a a i ; [10] [22] [13] xijuyslvbczgnmqwotfrdhpaek\n",
+      "9 :: a a j ; [10] [22] [14] lfzrwbytjisaovmuxdkhpneqgc\n",
+      "10 :: a a k ; [10] [22] [15] tkezcqynuwbpvhslfxoaimjrgd\n",
+      "11 :: a a l ; [10] [22] [16] kiwfnduxbsaotelqpvjmgrchzy\n",
+      "12 :: a a m ; [10] [22] [17] sfkutbpoxycrnmhgwlaedzqijv\n",
+      "13 :: a a n ; [10] [22] [18] baqwlkhgrsfextpocijnvudmzy\n",
+      "14 :: a a o ; [10] [22] [19] teofbdzxqkjyrscvimnawpuhlg\n",
+      "15 :: a a p ; [10] [22] [20] mhypswrbzxqvaondkgeutlfjci\n",
+      "16 :: a a q ; [10] [22] [21] cpasnrhgkuixzevbyfdwjotlqm\n",
+      "17 :: a a r ; [10] [22] [22] dlfatcjwygvbnmzrxpueskhqio\n",
+      "18 :: a a s ; [10] [22] [23] lxymzjuqtfpadsrkhonigwvbce\n",
+      "19 :: a a t ; [10] [22] [24] puvioztjdhxmlyeawsrgbcqknf\n",
+      "20 :: a a u ; [10] [22] [25] baigpldqcowfyzjehvtsxrkumn\n",
+      "21 :: a a v ; [10] [22] [0] mnvfydiwgzsoablrxpkutchqej\n",
+      "22 :: a b w ; [10] [23] [1] ulfopcykswhbzvderqixanjtgm\n",
+      "23 :: a b x ; [10] [23] [2] qmwftdyovursbzhxaklejicpgn\n",
+      "24 :: a b y ; [10] [23] [3] oljmzxrvucybdqasngpwihtfke\n",
+      "25 :: a b z ; [10] [23] [4] fwevcalzxutgysrqponkjdbimh\n"
      ]
     }
    ],
    "source": [
+    "# check the middle wheel turns over\n",
     "enigma.set_wheels('a', 'a', 'a')\n",
     "for i in range(26):\n",
     "    print(i, '::', \n",
     "          enigma.left_wheel.position_l, enigma.middle_wheel.position_l, enigma.right_wheel.position_l, ';',\n",
-    "          enigma.left_wheel.peg_positions, enigma.middle_wheel.peg_positions, enigma.right_wheel.peg_positions, \n",
+    "          enigma.left_wheel.notch_positions, enigma.middle_wheel.notch_positions, enigma.right_wheel.notch_positions, \n",
     "         cat(enigma.lookup(l) for l in string.ascii_lowercase))\n",
     "    enigma.advance()"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Formal test of middle wheel turnover"
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 778,
+   "execution_count": 179,
    "metadata": {
-    "collapsed": false,
+    "collapsed": true,
     "scrolled": true
    },
    "outputs": [],
     "enigma.set_wheels('a', 'a', 't')\n",
     "assert(enigma.wheel_positions == (0, 0, 19))\n",
     "assert(cat(enigma.wheel_positions_l) == 'aat')\n",
-    "assert(enigma.peg_positions == ([16], [4], [2]))\n",
+    "assert(enigma.notch_positions == ([10], [22], [24]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'puvioztjdhxmlyeawsrgbcqknf')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (0, 0, 20))\n",
     "assert(cat(enigma.wheel_positions_l) == 'aau')\n",
-    "assert(enigma.peg_positions == ([16], [4], [1]))\n",
+    "assert(enigma.notch_positions == ([10], [22], [25]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'baigpldqcowfyzjehvtsxrkumn')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (0, 0, 21))\n",
     "assert(cat(enigma.wheel_positions_l) == 'aav')\n",
-    "assert(enigma.peg_positions == ([16], [4], [0]))\n",
+    "assert(enigma.notch_positions == ([10], [22], [0]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'mnvfydiwgzsoablrxpkutchqej')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (0, 1, 22))\n",
     "assert(cat(enigma.wheel_positions_l) == 'abw')\n",
-    "assert(enigma.peg_positions == ([16], [3], [25]))\n",
+    "assert(enigma.notch_positions == ([10], [23], [1]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ulfopcykswhbzvderqixanjtgm')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (0, 1, 23))\n",
     "assert(cat(enigma.wheel_positions_l) == 'abx')\n",
-    "assert(enigma.peg_positions == ([16], [3], [24]))\n",
+    "assert(enigma.notch_positions == ([10], [23], [2]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'qmwftdyovursbzhxaklejicpgn')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (0, 1, 24))\n",
     "assert(cat(enigma.wheel_positions_l) == 'aby')\n",
-    "assert(enigma.peg_positions == ([16], [3], [23]))\n",
+    "assert(enigma.notch_positions == ([10], [23 ], [3]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'oljmzxrvucybdqasngpwihtfke')\n"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Test of middle wheel advancing the left wheel, exhibiting the \"double step\" behaviour."
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 779,
+   "execution_count": 180,
    "metadata": {
-    "collapsed": false,
     "scrolled": true
    },
    "outputs": [
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "(1, 5, 24) ('b', 'f', 'y') ([15], [25], [23]) baknstqzrmcxjdvygiefwoulph\n"
+      "(1, 5, 24) ('b', 'f', 'y') ([11], [1], [3]) baknstqzrmcxjdvygiefwoulph\n"
      ]
     }
    ],
     "enigma.set_wheels('a', 'd', 't')\n",
     "assert(enigma.wheel_positions == (0, 3, 19))\n",
     "assert(cat(enigma.wheel_positions_l) == 'adt')\n",
-    "assert(enigma.peg_positions == ([16], [1], [2]))\n",
+    "assert(enigma.notch_positions == ([10], [25], [24]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'zcbpqxwsjiuonmldethrkygfva')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (0, 3, 20))\n",
     "assert(cat(enigma.wheel_positions_l) == 'adu')\n",
-    "assert(enigma.peg_positions == ([16], [1], [1]))\n",
+    "assert(enigma.notch_positions == ([10], [25], [25]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ehprawjbngotxikcsdqlzyfmvu')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (0, 3, 21))\n",
     "assert(cat(enigma.wheel_positions_l) == 'adv')\n",
-    "assert(enigma.peg_positions == ([16], [1], [0]))\n",
+    "assert(enigma.notch_positions == ([10], [25], [0]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'eqzxarpihmnvjkwgbfuyslodtc')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (0, 4, 22))\n",
     "assert(cat(enigma.wheel_positions_l) == 'aew')\n",
-    "assert(enigma.peg_positions == ([16], [0], [25]))\n",
+    "assert(enigma.notch_positions == ([10], [0], [1]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'qedcbtpluzmhkongavwfirsyxj')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (1, 5, 23))\n",
     "assert(cat(enigma.wheel_positions_l) == 'bfx')\n",
-    "assert(enigma.peg_positions == ([15], [25], [24]))\n",
+    "assert(enigma.notch_positions == ([11], [1], [2]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'iwuedhsfazqxytvrkpgncoblmj')\n",
     "\n",
     "enigma.advance()\n",
     "assert(enigma.wheel_positions == (1, 5, 24))\n",
     "assert(cat(enigma.wheel_positions_l) == 'bfy')\n",
-    "assert(enigma.peg_positions == ([15], [25], [23]))\n",
+    "assert(enigma.notch_positions == ([11], [1], [3]))\n",
     "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'baknstqzrmcxjdvygiefwoulph')\n",
     "\n",
-    "print(enigma.wheel_positions, enigma.wheel_positions_l, enigma.peg_positions, \n",
+    "print(enigma.wheel_positions, enigma.wheel_positions_l, enigma.notch_positions, \n",
     "         cat(enigma.lookup(l) for l in string.ascii_lowercase))\n"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 780,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 181,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'olpfhnvflyn'"
       ]
      },
-     "execution_count": 780,
+     "execution_count": 181,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 781,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 182,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'lawnjgpwjik'"
       ]
      },
-     "execution_count": 781,
+     "execution_count": 182,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 782,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 183,
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (0, 3, 20))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'adu')\n",
+      "assert(enigma.notch_positions == ([10], [25], [25]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ehprawjbngotxikcsdqlzyfmvu')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (0, 3, 21))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'adv')\n",
+      "assert(enigma.notch_positions == ([10], [25], [0]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'eqzxarpihmnvjkwgbfuyslodtc')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (0, 4, 22))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'aew')\n",
+      "assert(enigma.notch_positions == ([10], [0], [1]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'qedcbtpluzmhkongavwfirsyxj')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (1, 5, 23))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'bfx')\n",
+      "assert(enigma.notch_positions == ([11], [1], [2]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'iwuedhsfazqxytvrkpgncoblmj')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (1, 5, 24))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'bfy')\n",
+      "assert(enigma.notch_positions == ([11], [1], [3]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'baknstqzrmcxjdvygiefwoulph')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (1, 5, 25))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'bfz')\n",
+      "assert(enigma.notch_positions == ([11], [1], [4]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'mudcgteyjiwravxzslqfbnkohp')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (1, 5, 0))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'bfa')\n",
+      "assert(enigma.notch_positions == ([11], [1], [5]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'gjkuotarmbcziwesvhpfdqnyxl')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (1, 5, 1))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'bfb')\n",
+      "assert(enigma.notch_positions == ([11], [1], [6]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'fcbmpaqihxytdrvegnwlzosjku')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (1, 5, 2))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'bfc')\n",
+      "assert(enigma.notch_positions == ([11], [1], [7]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'jktrlpmywabegzqfodxcvuishn')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (1, 5, 3))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'bfd')\n",
+      "assert(enigma.notch_positions == ([11], [1], [8]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'baetclivgurfzqponkxdjhyswm')\n",
+      "\n",
+      "enigma.advance()\n",
+      "assert(enigma.wheel_positions == (1, 5, 4))\n",
+      "assert(cat(enigma.wheel_positions_l) == 'bfe')\n",
+      "assert(enigma.notch_positions == ([11], [1], [9]))\n",
+      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'wvjlkpzxtcedqsyfmunirbahog')\n",
+      "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 5))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bff')\n",
-      "assert(enigma.peg_positions == ([15], [25], [16]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [10]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'zpqiogfsdlmjkyebcvhxwrutna')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 6))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfg')\n",
-      "assert(enigma.peg_positions == ([15], [25], [15]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [11]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'fjmnwayslbxicdpouthrqzekgv')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 7))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfh')\n",
-      "assert(enigma.peg_positions == ([15], [25], [14]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [12]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'csafzdyloxuhnmitwvbpkrqjge')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 8))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfi')\n",
-      "assert(enigma.peg_positions == ([15], [25], [13]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [13]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'kihyvulcbtagwrqzonxjfemsdp')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 9))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfj')\n",
-      "assert(enigma.peg_positions == ([15], [25], [12]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [14]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'pgzrytbksqhwxvuajdifonlmec')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 10))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfk')\n",
-      "assert(enigma.peg_positions == ([15], [25], [11]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [15]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'fkirsazncwbvyhpoudexqljtmg')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 11))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfl')\n",
-      "assert(enigma.peg_positions == ([15], [25], [10]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [16]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'mhkronubsvctafeqpdilgjxwzy')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 12))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfm')\n",
-      "assert(enigma.peg_positions == ([15], [25], [9]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [17]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'gnkuoxarzycmlbetvhwpdqsfji')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 13))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfn')\n",
-      "assert(enigma.peg_positions == ([15], [25], [8]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [18]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'bainslqkcxhfudpogtermwvjzy')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 14))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfo')\n",
-      "assert(enigma.peg_positions == ([15], [25], [7]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [19]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'xemfbdnwjitycgzusvqkprhalo')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 15))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfp')\n",
-      "assert(enigma.peg_positions == ([15], [25], [6]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [20]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'qixksmhgbtdvfonrapejwluczy')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 16))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfq')\n",
-      "assert(enigma.peg_positions == ([15], [25], [5]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [21]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'cgaulmbskwiefrtzynhodxjvqp')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 17))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfr')\n",
-      "assert(enigma.peg_positions == ([15], [25], [4]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [22]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'iwqfldszaxvenmyrcpgutkbjoh')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 18))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bfs')\n",
-      "assert(enigma.peg_positions == ([15], [25], [3]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [23]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'vxykrjilgfdhqtusmepnoazbcw')\n",
       "\n",
       "enigma.advance()\n",
       "assert(enigma.wheel_positions == (1, 5, 19))\n",
       "assert(cat(enigma.wheel_positions_l) == 'bft')\n",
-      "assert(enigma.peg_positions == ([15], [25], [2]))\n",
+      "assert(enigma.notch_positions == ([11], [1], [24]))\n",
       "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ieysbvkjahgmlpxnwtdrzfqocu')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 5, 20))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bfu')\n",
-      "assert(enigma.peg_positions == ([15], [25], [1]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'baihkjvdcfepywsltxoqzgnrmu')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 5, 21))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bfv')\n",
-      "assert(enigma.peg_positions == ([15], [25], [0]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'bayjtrilgdshvzuwxfkeompqcn')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 22))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bgw')\n",
-      "assert(enigma.peg_positions == ([15], [24], [25]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'rszqohpfxyutvwegdablkmnijc')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 23))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bgx')\n",
-      "assert(enigma.peg_positions == ([15], [24], [24]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'nfoxhbzeyrwqpacmljtsvukdig')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 24))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bgy')\n",
-      "assert(enigma.peg_positions == ([15], [24], [23]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'czaogmeihtuqfsdxlwnjkyrpvb')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 25))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bgz')\n",
-      "assert(enigma.peg_positions == ([15], [24], [22]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'omwgysdjkhizbxarupfvqtcnel')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 0))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bga')\n",
-      "assert(enigma.peg_positions == ([15], [24], [21]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'cxafmdrzoqutepinjgvlksybwh')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 1))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bgb')\n",
-      "assert(enigma.peg_positions == ([15], [24], [20]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'jymvnrxkoahwceiuzftspdlgbq')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 2))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bgc')\n",
-      "assert(enigma.peg_positions == ([15], [24], [19]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'uzlyiqwrestcnmxvfhjkapgodb')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 3))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bgd')\n",
-      "assert(enigma.peg_positions == ([15], [24], [18]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'veosbuhgpzqynmcikwdxfartlj')\n",
-      "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (1, 6, 4))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'bge')\n",
-      "assert(enigma.peg_positions == ([15], [24], [17]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ydhbmtrclxsiezpougkfqwvjan')\n",
       "\n"
      ]
     }
    ],
    "source": [
-    "\n",
+    "enigma.set_wheels('a', 'd', 't')\n",
     "for i in range(26):\n",
     "    enigma.advance()\n",
     "    print('enigma.advance()')\n",
     "    print(\"assert(enigma.wheel_positions == {})\".format(enigma.wheel_positions))\n",
     "    print(\"assert(cat(enigma.wheel_positions_l) == '{}')\".format(cat(enigma.wheel_positions_l)))\n",
-    "    print(\"assert(enigma.peg_positions == {})\".format(enigma.peg_positions))\n",
+    "    print(\"assert(enigma.notch_positions == {})\".format(enigma.notch_positions))\n",
     "    print(\"assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == '{}')\".format(cat(enigma.lookup(l) for l in string.ascii_lowercase)))\n",
     "    print()"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 783,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 184,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'bahxvfrpdc'"
       ]
      },
-     "execution_count": 783,
+     "execution_count": 184,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 784,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 185,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'kvmmwrlqlqsqpeugjrcxzwpfyiyybwloewrouvkpoztceuwtfjzqwpbqldttsr'"
       ]
      },
-     "execution_count": 784,
+     "execution_count": 185,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 785,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 186,
+   "metadata": {},
    "outputs": [
     {
      "data": {
        "'c'"
       ]
      },
-     "execution_count": 785,
+     "execution_count": 186,
      "metadata": {},
      "output_type": "execute_result"
     }
   },
   {
    "cell_type": "code",
-   "execution_count": 786,
+   "execution_count": 187,
    "metadata": {
     "collapsed": true
    },
     "# Enigma simulation settings are \n",
     "# http://enigma.louisedade.co.uk/enigma.html?m3;b;b153;AFTX;AJFE;AU-BG-EY-FP-HL-IN-JZ-OS-QR-TX\n",
     "w_enigma = Enigma(reflector_b_spec, \n",
-    "                wheel_i_spec, wheel_i_pegs,\n",
-    "                wheel_v_spec, wheel_v_pegs,\n",
-    "                wheel_iii_spec, wheel_iii_pegs,\n",
+    "                wheel_i_spec, wheel_i_notches,\n",
+    "                wheel_v_spec, wheel_v_notches,\n",
+    "                wheel_iii_spec, wheel_iii_notches,\n",
     "                6, 20, 24,\n",
     "                'ua pf rq so ni ey bg hl tx zj')"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 787,
+   "execution_count": 188,
    "metadata": {
     "collapsed": true
    },
    "outputs": [],
    "source": [
-    "# Setting sheet line 31 from http://www.codesandciphers.org.uk/enigma/enigma3.htm\n",
-    "# Enigma simulation settings are \n",
-    "# http://enigma.louisedade.co.uk/enigma.html?m3;b;b153;AFTX;AJFE;AU-BG-EY-FP-HL-IN-JZ-OS-QR-TX\n",
-    "enigma = Enigma(reflector_b_spec, \n",
-    "                wheel_i_spec, wheel_i_pegs,\n",
-    "                wheel_v_spec, wheel_v_pegs,\n",
-    "                wheel_iii_spec, wheel_iii_pegs,\n",
-    "                6, 20, 24,\n",
-    "                'ua pf rq so ni ey bg hl tx zj')"
+    "# Setting sheet line 31 from http://www.codesandciphers.org.uk/enigma/enigma3.htm\n",
+    "# Enigma simulation settings are \n",
+    "# http://enigma.louisedade.co.uk/enigma.html?m3;b;b153;AFTX;AJFE;AU-BG-EY-FP-HL-IN-JZ-OS-QR-TX\n",
+    "enigma = Enigma(reflector_b_spec, \n",
+    "#                 wheel_i_spec, wheel_i_notches,\n",
+    "#                 wheel_v_spec, wheel_v_notches,\n",
+    "#                 wheel_iii_spec, wheel_iii_notches,\n",
+    "                6, 20, 24,\n",
+    "                'ua pf rq so ni ey bg hl tx zj')"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 788,
+   "execution_count": 189,
    "metadata": {
     "collapsed": true
    },
    "outputs": [],
    "source": [
-    "enigma.set_wheels('j', 'e', 'u')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (4, 11, 24))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'jev')\n",
-    "assert(enigma.peg_positions == ([7], [21], [0]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'mvqjlyowkdieasgzcunxrbhtfp')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (4, 12, 25))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'jfw')\n",
-    "assert(enigma.peg_positions == ([7], [20], [25]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'sjolzuyvrbwdpxcmtiaqfhknge')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (4, 12, 0))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'jfx')\n",
-    "assert(enigma.peg_positions == ([7], [20], [24]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'qrxedkoywufmlvgsabpzjnicht')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (4, 12, 1))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'jfy')\n",
-    "assert(enigma.peg_positions == ([7], [20], [23]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'hpsukliagqefwvtbjxcodnmrzy')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (4, 12, 2))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'jfz')\n",
-    "assert(enigma.peg_positions == ([7], [20], [22]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'zevnbpyqowrtxdifhkulscjmga')\n"
+    "w_enigma.set_wheels('j', 'e', 'u')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (4, 11, 24))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'jev')\n",
+    "assert(w_enigma.notch_positions == ([19], [5], [0]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'mvqjlyowkdieasgzcunxrbhtfp')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (4, 12, 25))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'jfw')\n",
+    "assert(w_enigma.notch_positions == ([19], [6], [1]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'sjolzuyvrbwdpxcmtiaqfhknge')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (4, 12, 0))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'jfx')\n",
+    "assert(w_enigma.notch_positions == ([19], [6], [2]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'qrxedkoywufmlvgsabpzjnicht')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (4, 12, 1))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'jfy')\n",
+    "assert(w_enigma.notch_positions == ([19], [6], [3]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'hpsukliagqefwvtbjxcodnmrzy')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (4, 12, 2))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'jfz')\n",
+    "assert(w_enigma.notch_positions == ([19], [6], [4]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'zevnbpyqowrtxdifhkulscjmga')\n"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 789,
+   "execution_count": 190,
    "metadata": {
     "collapsed": true
    },
    "outputs": [],
    "source": [
-    "enigma.set_wheels('i', 'd', 'z')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 3))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'ida')\n",
-    "assert(enigma.peg_positions == ([8], [22], [21]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ikhpqrvcambzjondefwyxgsutl')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 4))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idb')\n",
-    "assert(enigma.peg_positions == ([8], [22], [20]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'cdabskhgzwfmlqvunyexpojtri')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 5))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idc')\n",
-    "assert(enigma.peg_positions == ([8], [22], [19]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'pcbwiqhgemyvjsuaftnroldzkx')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 6))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idd')\n",
-    "assert(enigma.peg_positions == ([8], [22], [18]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'xcbfvdnouptmlghjzwykierasq')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 7))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'ide')\n",
-    "assert(enigma.peg_positions == ([8], [22], [17]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'xfvglbdynuseriwqpmkzjcoaht')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 8))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idf')\n",
-    "assert(enigma.peg_positions == ([8], [22], [16]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'tfpqlbouynsewjgcdxkahzmriv')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 9))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idg')\n",
-    "assert(enigma.peg_positions == ([8], [22], [15]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'cjaunvlwtbygzexrspqidfhokm')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 10))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idh')\n",
-    "assert(enigma.peg_positions == ([8], [22], [14]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'yltxkrqvowebzpingfucshjdam')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 11))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idi')\n",
-    "assert(enigma.peg_positions == ([8], [22], [13]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'myktluzrnxceaiqsohpdfwvjbg')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 12))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idj')\n",
-    "assert(enigma.peg_positions == ([8], [22], [12]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'pynjrmiugdqxfcvakewzhoslbt')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 13))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idk')\n",
-    "assert(enigma.peg_positions == ([8], [22], [11]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'mwvedyplnoxhaijgrqtszcbkfu')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 14))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idl')\n",
-    "assert(enigma.peg_positions == ([8], [22], [10]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'qcbrfeutvoxpnmjladzhgiykws')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 15))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idm')\n",
-    "assert(enigma.peg_positions == ([8], [22], [9]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'dnoahryetsmukbcvwfjilpqzgx')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 16))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idn')\n",
-    "assert(enigma.peg_positions == ([8], [22], [8]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'nidcfehgbqsovalyjzkxwmutpr')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 17))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'ido')\n",
-    "assert(enigma.peg_positions == ([8], [22], [7]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'joifxdulcarhzpbntkwqgysevm')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 18))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idp')\n",
-    "assert(enigma.peg_positions == ([8], [22], [6]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ptnlsxvozmwdjchayuebrgkfqi')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 19))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idq')\n",
-    "assert(enigma.peg_positions == ([8], [22], [5]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'slwopzqnmxybihdeguavrtcjkf')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 20))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idr')\n",
-    "assert(enigma.peg_positions == ([8], [22], [4]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'hcbedwlamzogixkytsrqvufnpj')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 21))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'ids')\n",
-    "assert(enigma.peg_positions == ([8], [22], [3]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'odxbjwzrmelkisavuhnyqpfctg')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 22))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idt')\n",
-    "assert(enigma.peg_positions == ([8], [22], [2]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'udgbfeclrwnhxksvtioqapjmzy')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 23))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idu')\n",
-    "assert(enigma.peg_positions == ([8], [22], [1]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'nrdczqxmowvshaiufblypkjgte')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 10, 24))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'idv')\n",
-    "assert(enigma.peg_positions == ([8], [22], [0]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'hkifjdoacebqtzgulyvmpsxwrn')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 11, 25))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'iew')\n",
-    "assert(enigma.peg_positions == ([8], [21], [25]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'yptzuhofqvnmlkgbixwcejsrad')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 11, 0))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'iex')\n",
-    "assert(enigma.peg_positions == ([8], [21], [24]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'vkdcwhqfjibzsptngumoraeyxl')\n",
-    "\n",
-    "enigma.advance()\n",
-    "assert(enigma.wheel_positions == (3, 11, 1))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'iey')\n",
-    "assert(enigma.peg_positions == ([8], [21], [23]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'wenpbqrouxlkychdfgzvitajms')\n"
+    "w_enigma.set_wheels('i', 'd', 'z')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 3))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'ida')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [5]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'ikhpqrvcambzjondefwyxgsutl')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 4))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idb')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [6]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'cdabskhgzwfmlqvunyexpojtri')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 5))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idc')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [7]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'pcbwiqhgemyvjsuaftnroldzkx')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 6))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idd')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [8]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'xcbfvdnouptmlghjzwykierasq')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 7))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'ide')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [9]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'xfvglbdynuseriwqpmkzjcoaht')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 8))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idf')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [10]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'tfpqlbouynsewjgcdxkahzmriv')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 9))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idg')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [11]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'cjaunvlwtbygzexrspqidfhokm')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 10))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idh')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [12]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'yltxkrqvowebzpingfucshjdam')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 11))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idi')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [13]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'myktluzrnxceaiqsohpdfwvjbg')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 12))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idj')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [14]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'pynjrmiugdqxfcvakewzhoslbt')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 13))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idk')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [15]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'mwvedyplnoxhaijgrqtszcbkfu')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 14))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idl')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [16]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'qcbrfeutvoxpnmjladzhgiykws')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 15))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idm')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [17]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'dnoahryetsmukbcvwfjilpqzgx')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 16))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idn')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [18]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'nidcfehgbqsovalyjzkxwmutpr')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 17))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'ido')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [19]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'joifxdulcarhzpbntkwqgysevm')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 18))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idp')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [20]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'ptnlsxvozmwdjchayuebrgkfqi')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 19))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idq')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [21]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'slwopzqnmxybihdeguavrtcjkf')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 20))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idr')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [22]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'hcbedwlamzogixkytsrqvufnpj')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 21))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'ids')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [23]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'odxbjwzrmelkisavuhnyqpfctg')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 22))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idt')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [24]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'udgbfeclrwnhxksvtioqapjmzy')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 23))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idu')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [25]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'nrdczqxmowvshaiufblypkjgte')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 10, 24))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'idv')\n",
+    "assert(w_enigma.notch_positions == ([18], [4], [0]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'hkifjdoacebqtzgulyvmpsxwrn')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 11, 25))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'iew')\n",
+    "assert(w_enigma.notch_positions == ([18], [5], [1]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'yptzuhofqvnmlkgbixwcejsrad')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 11, 0))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'iex')\n",
+    "assert(w_enigma.notch_positions == ([18], [5], [2]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'vkdcwhqfjibzsptngumoraeyxl')\n",
+    "\n",
+    "w_enigma.advance()\n",
+    "assert(w_enigma.wheel_positions == (3, 11, 1))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'iey')\n",
+    "assert(w_enigma.notch_positions == ([18], [5], [3]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'wenpbqrouxlkychdfgzvitajms')\n"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 790,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 191,
+   "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "('verylongtestmessagewithanextrabitofmessageforgoodmeasure',\n",
-       " (3, 12, 6),\n",
-       " ('i', 'f', 'd'),\n",
-       " ([8], [20], [18]),\n",
-       " 'urygzpdmxtwshqvfnbljaokice')"
+       "([18], [5], [3])"
       ]
      },
-     "execution_count": 790,
+     "execution_count": 191,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "enigma.set_wheels('i', 'd', 'z')\n",
-    "ct = enigma.encipher('verylongtestmessagewithanextrabitofmessageforgoodmeasure')\n",
-    "assert(ct == 'gstsegeqdrthkfwesljjomfvcqwcfspxpfqqmewvddybarzwubxtpejz')\n",
-    "assert(enigma.wheel_positions == (3, 12, 6))\n",
-    "assert(cat(enigma.wheel_positions_l) == 'ifd')\n",
-    "assert(enigma.peg_positions == ([8], [20], [18]))\n",
-    "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'urygzpdmxtwshqvfnbljaokice')\n",
+    "w_enigma.notch_positions"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 192,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "('verylongtestmessagewithanextrabitofmessageforgoodmeasure',\n",
+       " (3, 12, 6),\n",
+       " ('i', 'f', 'd'),\n",
+       " ([18], [6], [8]),\n",
+       " 'urygzpdmxtwshqvfnbljaokice')"
+      ]
+     },
+     "execution_count": 192,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "w_enigma.set_wheels('i', 'd', 'z')\n",
+    "ct = w_enigma.encipher('verylongtestmessagewithanextrabitofmessageforgoodmeasure')\n",
+    "assert(ct == 'gstsegeqdrthkfwesljjomfvcqwcfspxpfqqmewvddybarzwubxtpejz')\n",
+    "assert(w_enigma.wheel_positions == (3, 12, 6))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'ifd')\n",
+    "assert(w_enigma.notch_positions == ([18], [6], [8]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'urygzpdmxtwshqvfnbljaokice')\n",
     "\n",
-    "enigma.set_wheels('i', 'd', 'z')\n",
-    "pt = enigma.encipher('gstsegeqdrthkfwesljjomfvcqwcfspxpfqqmewvddybarzwubxtpejz')\n",
+    "w_enigma.set_wheels('i', 'd', 'z')\n",
+    "pt = w_enigma.encipher('gstsegeqdrthkfwesljjomfvcqwcfspxpfqqmewvddybarzwubxtpejz')\n",
     "assert(pt == 'verylongtestmessagewithanextrabitofmessageforgoodmeasure')\n",
     "\n",
-    "pt, enigma.wheel_positions, enigma.wheel_positions_l, enigma.peg_positions, cat(enigma.lookup(l) for l in string.ascii_lowercase)"
+    "pt, w_enigma.wheel_positions, w_enigma.wheel_positions_l, w_enigma.notch_positions, cat(w_enigma.lookup(l) for l in string.ascii_lowercase)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 791,
-   "metadata": {
-    "collapsed": false
-   },
+   "execution_count": 193,
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 3))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'ida')\n",
-      "assert(enigma.peg_positions == ([8], [22], [21]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ikhpqrvcambzjondefwyxgsutl')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 3))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'ida')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [5]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'ikhpqrvcambzjondefwyxgsutl')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 4))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idb')\n",
-      "assert(enigma.peg_positions == ([8], [22], [20]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'cdabskhgzwfmlqvunyexpojtri')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 4))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idb')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [6]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'cdabskhgzwfmlqvunyexpojtri')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 5))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idc')\n",
-      "assert(enigma.peg_positions == ([8], [22], [19]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'pcbwiqhgemyvjsuaftnroldzkx')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 5))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idc')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [7]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'pcbwiqhgemyvjsuaftnroldzkx')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 6))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idd')\n",
-      "assert(enigma.peg_positions == ([8], [22], [18]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'xcbfvdnouptmlghjzwykierasq')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 6))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idd')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [8]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'xcbfvdnouptmlghjzwykierasq')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 7))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'ide')\n",
-      "assert(enigma.peg_positions == ([8], [22], [17]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'xfvglbdynuseriwqpmkzjcoaht')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 7))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'ide')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [9]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'xfvglbdynuseriwqpmkzjcoaht')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 8))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idf')\n",
-      "assert(enigma.peg_positions == ([8], [22], [16]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'tfpqlbouynsewjgcdxkahzmriv')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 8))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idf')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [10]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'tfpqlbouynsewjgcdxkahzmriv')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 9))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idg')\n",
-      "assert(enigma.peg_positions == ([8], [22], [15]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'cjaunvlwtbygzexrspqidfhokm')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 9))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idg')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [11]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'cjaunvlwtbygzexrspqidfhokm')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 10))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idh')\n",
-      "assert(enigma.peg_positions == ([8], [22], [14]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'yltxkrqvowebzpingfucshjdam')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 10))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idh')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [12]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'yltxkrqvowebzpingfucshjdam')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 11))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idi')\n",
-      "assert(enigma.peg_positions == ([8], [22], [13]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'myktluzrnxceaiqsohpdfwvjbg')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 11))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idi')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [13]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'myktluzrnxceaiqsohpdfwvjbg')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 12))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idj')\n",
-      "assert(enigma.peg_positions == ([8], [22], [12]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'pynjrmiugdqxfcvakewzhoslbt')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 12))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idj')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [14]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'pynjrmiugdqxfcvakewzhoslbt')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 13))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idk')\n",
-      "assert(enigma.peg_positions == ([8], [22], [11]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'mwvedyplnoxhaijgrqtszcbkfu')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 13))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idk')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [15]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'mwvedyplnoxhaijgrqtszcbkfu')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 14))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idl')\n",
-      "assert(enigma.peg_positions == ([8], [22], [10]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'qcbrfeutvoxpnmjladzhgiykws')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 14))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idl')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [16]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'qcbrfeutvoxpnmjladzhgiykws')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 15))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idm')\n",
-      "assert(enigma.peg_positions == ([8], [22], [9]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'dnoahryetsmukbcvwfjilpqzgx')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 15))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idm')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [17]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'dnoahryetsmukbcvwfjilpqzgx')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 16))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idn')\n",
-      "assert(enigma.peg_positions == ([8], [22], [8]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'nidcfehgbqsovalyjzkxwmutpr')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 16))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idn')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [18]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'nidcfehgbqsovalyjzkxwmutpr')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 17))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'ido')\n",
-      "assert(enigma.peg_positions == ([8], [22], [7]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'joifxdulcarhzpbntkwqgysevm')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 17))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'ido')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [19]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'joifxdulcarhzpbntkwqgysevm')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 18))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idp')\n",
-      "assert(enigma.peg_positions == ([8], [22], [6]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'ptnlsxvozmwdjchayuebrgkfqi')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 18))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idp')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [20]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'ptnlsxvozmwdjchayuebrgkfqi')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 19))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idq')\n",
-      "assert(enigma.peg_positions == ([8], [22], [5]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'slwopzqnmxybihdeguavrtcjkf')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 19))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idq')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [21]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'slwopzqnmxybihdeguavrtcjkf')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 20))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idr')\n",
-      "assert(enigma.peg_positions == ([8], [22], [4]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'hcbedwlamzogixkytsrqvufnpj')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 20))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idr')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [22]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'hcbedwlamzogixkytsrqvufnpj')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 21))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'ids')\n",
-      "assert(enigma.peg_positions == ([8], [22], [3]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'odxbjwzrmelkisavuhnyqpfctg')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 21))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'ids')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [23]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'odxbjwzrmelkisavuhnyqpfctg')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 22))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idt')\n",
-      "assert(enigma.peg_positions == ([8], [22], [2]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'udgbfeclrwnhxksvtioqapjmzy')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 22))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idt')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [24]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'udgbfeclrwnhxksvtioqapjmzy')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 23))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idu')\n",
-      "assert(enigma.peg_positions == ([8], [22], [1]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'nrdczqxmowvshaiufblypkjgte')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 23))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idu')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [25]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'nrdczqxmowvshaiufblypkjgte')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 10, 24))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'idv')\n",
-      "assert(enigma.peg_positions == ([8], [22], [0]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'hkifjdoacebqtzgulyvmpsxwrn')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 10, 24))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'idv')\n",
+      "assert(w_enigma.notch_positions == ([18], [4], [0]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'hkifjdoacebqtzgulyvmpsxwrn')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 11, 25))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'iew')\n",
-      "assert(enigma.peg_positions == ([8], [21], [25]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'yptzuhofqvnmlkgbixwcejsrad')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 11, 25))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'iew')\n",
+      "assert(w_enigma.notch_positions == ([18], [5], [1]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'yptzuhofqvnmlkgbixwcejsrad')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 11, 0))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'iex')\n",
-      "assert(enigma.peg_positions == ([8], [21], [24]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'vkdcwhqfjibzsptngumoraeyxl')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 11, 0))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'iex')\n",
+      "assert(w_enigma.notch_positions == ([18], [5], [2]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'vkdcwhqfjibzsptngumoraeyxl')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 11, 1))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'iey')\n",
-      "assert(enigma.peg_positions == ([8], [21], [23]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'wenpbqrouxlkychdfgzvitajms')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 11, 1))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'iey')\n",
+      "assert(w_enigma.notch_positions == ([18], [5], [3]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'wenpbqrouxlkychdfgzvitajms')\n",
       "\n",
-      "enigma.advance()\n",
-      "assert(enigma.wheel_positions == (3, 11, 2))\n",
-      "assert(cat(enigma.wheel_positions_l) == 'iez')\n",
-      "assert(enigma.peg_positions == ([8], [21], [22]))\n",
-      "assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == 'szgyqvclkoihurjwenaxmfptdb')\n",
+      "w_enigma.advance()\n",
+      "assert(w_enigma.wheel_positions == (3, 11, 2))\n",
+      "assert(cat(w_enigma.wheel_positions_l) == 'iez')\n",
+      "assert(w_enigma.notch_positions == ([18], [5], [4]))\n",
+      "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'szgyqvclkoihurjwenaxmfptdb')\n",
       "\n"
      ]
     }
    ],
    "source": [
-    "enigma.set_wheels('i', 'd', 'z')\n",
+    "w_enigma.set_wheels('i', 'd', 'z')\n",
     "\n",
     "for i in range(26):\n",
-    "    enigma.advance()\n",
-    "    print('enigma.advance()')\n",
-    "    print(\"assert(enigma.wheel_positions == {})\".format(enigma.wheel_positions))\n",
-    "    print(\"assert(cat(enigma.wheel_positions_l) == '{}')\".format(cat(enigma.wheel_positions_l)))\n",
-    "    print(\"assert(enigma.peg_positions == {})\".format(enigma.peg_positions))\n",
-    "    print(\"assert(cat(enigma.lookup(l) for l in string.ascii_lowercase) == '{}')\".format(cat(enigma.lookup(l) for l in string.ascii_lowercase)))\n",
+    "    w_enigma.advance()\n",
+    "    print('w_enigma.advance()')\n",
+    "    print(\"assert(w_enigma.wheel_positions == {})\".format(w_enigma.wheel_positions))\n",
+    "    print(\"assert(cat(w_enigma.wheel_positions_l) == '{}')\".format(cat(w_enigma.wheel_positions_l)))\n",
+    "    print(\"assert(w_enigma.notch_positions == {})\".format(w_enigma.notch_positions))\n",
+    "    print(\"assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == '{}')\".format(cat(w_enigma.lookup(l) for l in string.ascii_lowercase)))\n",
+    "    print()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 215,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "self.assertEqual(self.enigma31.wheel_positions, (21, 5, 22))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'ayt')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([10], [25], [24]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'izhrgtecaslkywvqpdjfxonumb')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (21, 5, 23))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'ayu')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([10], [25], [25]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'dtoavihgflwjnmcsrqpbzekyxu')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (21, 5, 24))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'ayv')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([10], [25], [0]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'xquhtpsdwkjonmlfbvgecriazy')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (21, 6, 25))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'azw')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([10], [0], [1]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'dofapcluvmngjkbezyxwhitsrq')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (22, 7, 0))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'bax')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([11], [1], [2]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'jdlbmswztapcexrkuofiqygnvh')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (22, 7, 1))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'bay')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([11], [1], [3]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'iydcnuhgawsoxelztvkqfrjmbp')\n",
+      "\n"
+     ]
+    }
+   ],
+   "source": [
+    "w_enigma.set_wheels('a', 'y', 't')\n",
+    "\n",
+    "print(\"self.assertEqual(self.enigma31.wheel_positions, {})\".format(w_enigma.wheel_positions))\n",
+    "print(\"self.assertEqual(cat(self.enigma31.wheel_positions_l), '{}')\".format(cat(w_enigma.wheel_positions_l)))\n",
+    "print(\"self.assertEqual(self.enigma31.notch_positions, {})\".format(w_enigma.notch_positions))\n",
+    "print(\"assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == '{}')\".format(cat(w_enigma.lookup(l) for l in string.ascii_lowercase)))\n",
+    "print()\n",
+    "\n",
+    "for i in range(5):\n",
+    "    w_enigma.advance()\n",
+    "    print('self.enigma31.advance()')\n",
+    "    print(\"self.assertEqual(self.enigma31.wheel_positions, {})\".format(w_enigma.wheel_positions))\n",
+    "    print(\"self.assertEqual(cat(self.enigma31.wheel_positions_l), '{}')\".format(cat(w_enigma.wheel_positions_l)))\n",
+    "    print(\"self.assertEqual(self.enigma31.notch_positions, {})\".format(w_enigma.notch_positions))\n",
+    "    print(\"assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == '{}')\".format(cat(w_enigma.lookup(l) for l in string.ascii_lowercase)))\n",
     "    print()"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 216,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "self.assertEqual(self.enigma31.wheel_positions, (21, 6, 22))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'azt')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([10], [0], [24]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'idjbptqwacsvnmregokfzlhyxu')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (22, 7, 23))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'bau')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([11], [1], [25]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'rniszouwcxtvqbfymadkglhjpe')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (22, 7, 24))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'bav')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([11], [1], [0]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'qijfsdmkbchugxtwazeolypnvr')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (22, 8, 25))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'bbw')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([11], [2], [1]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'xprtlozyskjewqfbncidvumahg')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (22, 8, 0))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'bbx')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([11], [2], [2]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'vtfuyczoqxmpkwhlisrbdanjeg')\n",
+      "\n",
+      "self.enigma31.advance()\n",
+      "self.assertEqual(self.enigma31.wheel_positions, (22, 8, 1))\n",
+      "self.assertEqual(cat(self.enigma31.wheel_positions_l), 'bby')\n",
+      "self.assertEqual(self.enigma31.notch_positions, ([11], [2], [3]))\n",
+      "assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == 'tjrhzpqdobwxyuifgcvansklme')\n",
+      "\n"
+     ]
+    }
+   ],
+   "source": [
+    "w_enigma.set_wheels('a', 'z', 't')\n",
+    "\n",
+    "print(\"self.assertEqual(self.enigma31.wheel_positions, {})\".format(w_enigma.wheel_positions))\n",
+    "print(\"self.assertEqual(cat(self.enigma31.wheel_positions_l), '{}')\".format(cat(w_enigma.wheel_positions_l)))\n",
+    "print(\"self.assertEqual(self.enigma31.notch_positions, {})\".format(w_enigma.notch_positions))\n",
+    "print(\"assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == '{}')\".format(cat(w_enigma.lookup(l) for l in string.ascii_lowercase)))\n",
+    "print()\n",
+    "\n",
+    "for i in range(5):\n",
+    "    w_enigma.advance()\n",
+    "    print('self.enigma31.advance()')\n",
+    "    print(\"self.assertEqual(self.enigma31.wheel_positions, {})\".format(w_enigma.wheel_positions))\n",
+    "    print(\"self.assertEqual(cat(self.enigma31.wheel_positions_l), '{}')\".format(cat(w_enigma.wheel_positions_l)))\n",
+    "    print(\"self.assertEqual(self.enigma31.notch_positions, {})\".format(w_enigma.notch_positions))\n",
+    "    print(\"assert(cat(self.enigma31.lookup(l) for l in string.ascii_lowercase) == '{}')\".format(cat(w_enigma.lookup(l) for l in string.ascii_lowercase)))\n",
+    "    print()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 221,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "w_enigma.set_wheels('i', 'z', 'd')\n",
+    "ct = w_enigma.encipher('verylongtestmessagewithanextrabitofmessageforgoodmeasure')\n",
+    "assert(ct == 'apocwtjuikurcfivlozvhffkoacxufcekthcvodfqpxdjqyckdozlqki')\n",
+    "assert(w_enigma.wheel_positions == (4, 9, 10))\n",
+    "assert(cat(w_enigma.wheel_positions_l) == 'jch')\n",
+    "assert(w_enigma.notch_positions == ([19], [3], [12]))\n",
+    "assert(cat(w_enigma.lookup(l) for l in string.ascii_lowercase) == 'mopnigfuesqwadbcktjrhylzvx')\n",
+    "\n",
+    "w_enigma.set_wheels('i', 'z', 'd')\n",
+    "pt = w_enigma.decipher('apocwtjuikurcfivlozvhffkoacxufcekthcvodfqpxdjqyckdozlqki')\n",
+    "assert(pt == 'verylongtestmessagewithanextrabitofmessageforgoodmeasure')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 218,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "([19], [3], [12])"
+      ]
+     },
+     "execution_count": 218,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "w_enigma.notch_positions"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 194,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "# Reflector B\n",
+    "# Rotors III, I, II with rings 17, 11, 19\n",
+    "# Plugboard pairs GU FZ BD LK TC PS HV WN JE AM\n",
+    "\n",
+    "tbt_enigma = Enigma(reflector_b_spec, \n",
+    "                wheel_iii_spec, wheel_iii_notches,\n",
+    "                wheel_i_spec, wheel_i_notches,\n",
+    "                wheel_ii_spec, wheel_ii_notches,\n",
+    "                17, 11, 19,\n",
+    "                'GU FZ BD LK TC PS HV WN JE AM'.lower())"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 195,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'jbvbwwzfslhxnhzzccsngebmrnswgjonwbjnzcfgadeuoyameylmpvny'"
+      ]
+     },
+     "execution_count": 195,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "tbt_enigma.set_wheels('a', 'q', 'v')\n",
+    "ct = tbt_enigma.encipher('very long test message with an extra bit of message for good measure')\n",
+    "ct"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 196,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'SLGNC SZXLT KZEBG HSTGY WDMPR'"
+      ]
+     },
+     "execution_count": 196,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "target_ct = 'SLGNC SZXLT KZEBG HSTGY WDMPR'\n",
+    "target_ct"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 197,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'Theyw erede tecte d byBri tishs hipsi nclud'"
+      ]
+     },
+     "execution_count": 197,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "target_pt = 'Theyw erede tecte d byBri tishs hipsi nclud'\n",
+    "target_pt"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 198,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(29, 43)"
+      ]
+     },
+     "execution_count": 198,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "len(target_ct), len(target_pt)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 199,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "SLGNC SZXLT KZEBG HSTGY WDMPR\n",
+      "Theyw erede tecte d byBri tishs hipsi nclud\n"
+     ]
+    }
+   ],
+   "source": [
+    "print('{}\\n{}'.format(target_ct, target_pt))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 200,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Theyw erede tecte d byBri tishs hipsi nclud\n",
+      "SLGNC SZXLT KZEBG HSTGY WDMPR\n",
+      "slgncszxltkzebghstgywdmprucuzqdqzpve\n",
+      "theyweredetectedbybritish\n"
+     ]
+    }
+   ],
+   "source": [
+    "tbt_enigma.set_wheels('a', 'a', 'a')\n",
+    "this_pt = tbt_enigma.encipher(target_ct)\n",
+    "\n",
+    "tbt_enigma.set_wheels('a', 'a', 'a')\n",
+    "this_ct = tbt_enigma.encipher(target_pt)\n",
+    "\n",
+    "\n",
+    "print('{}\\n{}\\n{}\\n{}'.format(target_pt, target_ct, this_ct, this_pt))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 201,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "import itertools"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 202,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "def str_ham(s1, s2):\n",
+    "    \"\"\"Hamming distance for strings\"\"\"\n",
+    "    return sum(1 for c1, c2 in zip(s1, s2) if c1 != c2)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 203,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "0"
+      ]
+     },
+     "execution_count": 203,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "str_ham('hello', 'hello')"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "A brute-force check of all message settings, looking for the one that generates the target text."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 204,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "best ('a', 'a', 'a') 29\n",
+      "best ('a', 'a', 'a') 29\n",
+      "best ('a', 'a', 'a') 29\n",
+      "best ('a', 'a', 'a') 29\n",
+      "1 loop, best of 3: 20.6 s per loop\n"
+     ]
+    }
+   ],
+   "source": [
+    "%%timeit\n",
+    "best = ('a', 'a', 'a')\n",
+    "best_hd = 10000\n",
+    "for w1, w2, w3 in itertools.product(string.ascii_lowercase, repeat=3):\n",
+    "    tbt_enigma.set_wheels(w1, w2, w3)\n",
+    "    this_ct = tbt_enigma.encipher(target_pt)\n",
+    "    if this_ct == target_ct:\n",
+    "        print(w1, w2, w3)\n",
+    "    if str_ham(this_ct, target_ct) < best_hd:\n",
+    "        best = (w1, w2, w3)\n",
+    "        best_hd = str_ham(this_ct, target_ct)\n",
+    "print('best', best, best_hd)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 205,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Wheels now ['a', 'a', 'b'] enciphering t -> s\n",
+      "Wheels now ['a', 'a', 'c'] enciphering h -> l\n",
+      "Wheels now ['a', 'a', 'd'] enciphering e -> g\n",
+      "Wheels now ['a', 'a', 'e'] enciphering y -> n\n",
+      "Wheels now ['a', 'b', 'f'] enciphering w -> c\n",
+      "Wheels now ['a', 'b', 'g'] enciphering e -> s\n",
+      "Wheels now ['a', 'b', 'h'] enciphering r -> z\n",
+      "Wheels now ['a', 'b', 'i'] enciphering e -> x\n",
+      "Wheels now ['a', 'b', 'j'] enciphering d -> l\n",
+      "Wheels now ['a', 'b', 'k'] enciphering e -> t\n",
+      "Wheels now ['a', 'b', 'l'] enciphering t -> k\n",
+      "Wheels now ['a', 'b', 'm'] enciphering e -> z\n",
+      "Wheels now ['a', 'b', 'n'] enciphering c -> e\n",
+      "Wheels now ['a', 'b', 'o'] enciphering t -> b\n",
+      "Wheels now ['a', 'b', 'p'] enciphering e -> g\n",
+      "Wheels now ['a', 'b', 'q'] enciphering d -> h\n",
+      "Wheels now ['a', 'b', 'r'] enciphering b -> s\n",
+      "Wheels now ['a', 'b', 's'] enciphering y -> t\n",
+      "Wheels now ['a', 'b', 't'] enciphering b -> g\n",
+      "Wheels now ['a', 'b', 'u'] enciphering r -> y\n",
+      "Wheels now ['a', 'b', 'v'] enciphering i -> w\n",
+      "Wheels now ['a', 'b', 'w'] enciphering t -> d\n",
+      "Wheels now ['a', 'b', 'x'] enciphering i -> m\n",
+      "Wheels now ['a', 'b', 'y'] enciphering s -> p\n",
+      "Wheels now ['a', 'b', 'z'] enciphering h -> r\n",
+      "Wheels now ['a', 'b', 'a'] enciphering s -> u\n",
+      "Wheels now ['a', 'b', 'b'] enciphering h -> c\n",
+      "Wheels now ['a', 'b', 'c'] enciphering i -> u\n",
+      "Wheels now ['a', 'b', 'd'] enciphering p -> z\n",
+      "Wheels now ['a', 'b', 'e'] enciphering s -> q\n",
+      "Wheels now ['a', 'c', 'f'] enciphering i -> d\n",
+      "Wheels now ['a', 'c', 'g'] enciphering n -> q\n",
+      "Wheels now ['a', 'c', 'h'] enciphering c -> z\n",
+      "Wheels now ['a', 'c', 'i'] enciphering l -> p\n",
+      "Wheels now ['a', 'c', 'j'] enciphering u -> v\n",
+      "Wheels now ['a', 'c', 'k'] enciphering d -> e\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "('slgncszxltkzebghstgywdmprucuzqdqzpve', 'SLGNC SZXLT KZEBG HSTGY WDMPR')"
+      ]
+     },
+     "execution_count": 205,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "tbt_enigma.set_wheels('a', 'a', 'a')\n",
+    "tbt_enigma.encipher(target_pt, debug=True), target_ct"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 206,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Wheels now ['a', 'a', 'b'] enciphering s -> t\n",
+      "Wheels now ['a', 'a', 'c'] enciphering l -> h\n",
+      "Wheels now ['a', 'a', 'd'] enciphering g -> e\n",
+      "Wheels now ['a', 'a', 'e'] enciphering n -> y\n",
+      "Wheels now ['a', 'b', 'f'] enciphering c -> w\n",
+      "Wheels now ['a', 'b', 'g'] enciphering s -> e\n",
+      "Wheels now ['a', 'b', 'h'] enciphering z -> r\n",
+      "Wheels now ['a', 'b', 'i'] enciphering x -> e\n",
+      "Wheels now ['a', 'b', 'j'] enciphering l -> d\n",
+      "Wheels now ['a', 'b', 'k'] enciphering t -> e\n",
+      "Wheels now ['a', 'b', 'l'] enciphering k -> t\n",
+      "Wheels now ['a', 'b', 'm'] enciphering z -> e\n",
+      "Wheels now ['a', 'b', 'n'] enciphering e -> c\n",
+      "Wheels now ['a', 'b', 'o'] enciphering b -> t\n",
+      "Wheels now ['a', 'b', 'p'] enciphering g -> e\n",
+      "Wheels now ['a', 'b', 'q'] enciphering h -> d\n",
+      "Wheels now ['a', 'b', 'r'] enciphering s -> b\n",
+      "Wheels now ['a', 'b', 's'] enciphering t -> y\n",
+      "Wheels now ['a', 'b', 't'] enciphering g -> b\n",
+      "Wheels now ['a', 'b', 'u'] enciphering y -> r\n",
+      "Wheels now ['a', 'b', 'v'] enciphering w -> i\n",
+      "Wheels now ['a', 'b', 'w'] enciphering d -> t\n",
+      "Wheels now ['a', 'b', 'x'] enciphering m -> i\n",
+      "Wheels now ['a', 'b', 'y'] enciphering p -> s\n",
+      "Wheels now ['a', 'b', 'z'] enciphering r -> h\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "('theyweredetectedbybritish', 'Theyw erede tecte d byBri tishs hipsi nclud')"
+      ]
+     },
+     "execution_count": 206,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "tbt_enigma.set_wheels('a', 'a', 'a')\n",
+    "tbt_enigma.encipher(target_ct, debug=True), target_pt"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 207,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "('theyweredetectedbybritish', 'Theyw erede tecte d byBri tishs hipsi nclud')"
+      ]
+     },
+     "execution_count": 207,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "tbt_enigma.set_wheels('a', 'a', 'a')\n",
+    "tbt_enigma.encipher(target_ct), target_pt"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 208,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'mdtbjzuvielkawosqrpcghnxyf'"
+      ]
+     },
+     "execution_count": 208,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "cat(tbt_enigma.plugboard.forward(l) for l in string.ascii_lowercase)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 209,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "10"
+      ]
+     },
+     "execution_count": 209,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "tbt_enigma.set_wheels('a', 'a', 'a')\n",
+    "tbt_enigma.left_wheel.position"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.5.1+"
+   "version": "3.5.3"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 0
+ "nbformat_minor": 1
 }