{
 "metadata": {
  "name": ""
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%autosave 10"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "javascript": [
        "IPython.notebook.set_autosave_interval(10000)"
       ],
       "metadata": {},
       "output_type": "display_data"
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Autosaving every 10 seconds\n"
       ]
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "(wait for IPython Notebook to get posted)  \n",
      "- !!AI look in 2013-talks, found a copy of the talk. go through it make notes."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "##\u00a0Background"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def f(x):\n",
      "    return x+1, x+2\n",
      "f(10) == (11, 12)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 2,
       "text": [
        "True"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def f(x):\n",
      "    yield x+1\n",
      "    yield x+2\n",
      "list(f(10)) == [11, 12]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 3,
       "text": [
        "True"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Generators require iteration over results."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Callable"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "class Callable(object):\n",
      "    def __call__(self, x):\n",
      "        return x+1, x+2\n",
      "Callable()(10) == (11, 12)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 4,
       "text": [
        "True"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Iterable\n",
      "\n",
      "- `__iter__`, `__next__`"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Generators\n",
      "\n",
      "At the C-level, generators are functions that leave state behind when yielding. It just jumps over the cleanup."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Coroutines\n",
      "\n",
      "- Functions have one entry, one exit, and eagerly return results.\n",
      "- Coroutines have multiple entries, multiple exits, and lazily return results.\n",
      "- `throw`, `send`, `close`.\n",
      "    - `throw`: throw exception during iteration.\n",
      "    - `close`: halt a generator, clean up state.\n",
      "    - `send`: send value back into a generator."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def generator(x):\n",
      "    y = None\n",
      "    y = yield x+1, y\n",
      "    y = yield x+1, y\n",
      "\n",
      "g = generator(10)\n",
      "print g.next()\n",
      "print g.send(\"abc\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "(11, None)\n",
        "(11, 'abc')\n"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Pumping and priming\n",
      "\n",
      "- One annoyance.\n",
      "- Can't inject value before first yield into a generator/coroutine.\n",
      "- \"Can't send non-None to a just-started generator\"\n",
      "- You'll see \"pump\" or \"prime\" decorator in large projects.\n",
      "\n",
      "## Itertools\n",
      "\n",
      "- 2nd out of 23 favourite Python modules.\n",
      "- Generators is one of the core features of Python.\n",
      "- `izip`, `islice` help you manipulate iterables without caring about their contents.\n",
      "    - e.g. can't concatenate a list and a tuple natively.\n",
      "    - but `chain` just connects iterables, doesn't care.\n",
      "- Want to dscompose problem into composition of streams, and don't need to bring everything into memory."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
 ]
}