Added itertools snippet.

core/functions.ipynb

@@ -1,7 +1,7 @@
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   "name": "",
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+  "signature": "sha256:7302df53c9f267690231320dc5731929b2c6969b01ff3cfc482e4708b66f2162"
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@@ -25,7 +25,8 @@
       "* \\*args, \\*\\*kwargs\n",
       "* Currying\n",
       "* Generators\n",
-      "* Generator Expressions"
+      "* Generator Expressions\n",
+      "* itertools"
      ]
     },
     {
@@ -512,6 +513,56 @@
       }
      ],
      "prompt_number": 11
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## itertools\n",
+      "\n",
+      "The library itertools has a collection of generators useful for data analysis.\n",
+      "\n",
+      "Function groupby takes a sequence and a key function, grouping consecutive elements in the sequence by the input function's return value (the key).  groupby returns the function's return value (the key) and a generator."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "import itertools\n",
+      "first_letter = lambda x: x[0]\n",
+      "strings = ['foo', 'bar', 'baz']\n",
+      "for letter, gen_names in itertools.groupby(strings, first_letter):\n",
+      "    print letter, list(gen_names)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "f ['foo']\n",
+        "b ['bar', 'baz']\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "itertools contains many other useful functions:\n",
+      "\n",
+      "| Function      | Description|\n",
+      "| ------------- |-------------|\n",
+      "| imap          | Generator version of map  |\n",
+      "| ifilter       | Generator version of filter      |\n",
+      "| combinations  | Generates a sequence of all possible k-tuples of elements in the iterable, ignoring order      |\n",
+      "| permutations  | Generates a sequence of all possible k-tuples of elements in the iterable, respecting order      |\n",
+      "| groupby       | Generates (key, sub-iterator) for each unique key      |"
+     ]
     }
    ],
    "metadata": {}