From bf1f35d7af9a0f7eb735407ad3b934c234fb4555 Mon Sep 17 00:00:00 2001
From: Donne Martin <donne.martin@gmail.com>
Date: Mon, 26 Jan 2015 13:00:12 -0500
Subject: [PATCH] Added comprehension snippets for list, dict, and set. 
 Tweaked a few snippets and content.

---
 core/structs_utils.ipynb | 168 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 158 insertions(+), 10 deletions(-)

diff --git a/core/structs_utils.ipynb b/core/structs_utils.ipynb
index d4979d7..227f002 100644
--- a/core/structs_utils.ipynb
+++ b/core/structs_utils.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:73ff6384d9af604860ac45769daf4ddad270f251d7838e691c99d5d419e0c72b"
+  "signature": "sha256:893799227c6632abab6f36b3299512e1f724d3a9e69a9cc0b81a3ff9c872f370"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -12,7 +12,7 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "# Data Structures Utilities"
+      "# Data Structure Utilities"
      ]
     },
     {
@@ -26,7 +26,8 @@
       "* sorted\n",
       "* reversed\n",
       "* enumerate\n",
-      "* zip"
+      "* zip\n",
+      "* list comprehensions"
      ]
     },
     {
@@ -666,9 +667,9 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "numbers = ['zero', 'one', 'two', 'three']\n",
-      "for i, number in enumerate(numbers):\n",
-      "    print(i, number)"
+      "strings = ['foo', 'bar', 'baz']\n",
+      "for i, string in enumerate(strings):\n",
+      "    print(i, string)"
      ],
      "language": "python",
      "metadata": {},
@@ -677,10 +678,9 @@
        "output_type": "stream",
        "stream": "stdout",
        "text": [
-        "(0, 'zero')\n",
-        "(1, 'one')\n",
-        "(2, 'two')\n",
-        "(3, 'three')\n"
+        "(0, 'foo')\n",
+        "(1, 'bar')\n",
+        "(2, 'baz')\n"
        ]
       }
      ],
@@ -827,6 +827,154 @@
       }
      ],
      "prompt_number": 27
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## List Comprehensions"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Concisely form a new list by filtering the elements of a sequence and transforming the elements passing the filter.  List comprehensions take the form:\n",
+      "```python\n",
+      "[expr for val in collection if condition]\n",
+      "```\n",
+      "Which is equivalent to the following for loop:\n",
+      "```python\n",
+      "result = []\n",
+      "for val in collection:\n",
+      "    if condition:\n",
+      "        result.append(expr)\n",
+      "```"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Convert to upper case all strings that start with a 'b'"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "strings = ['foo', 'bar', 'baz', 'f', 'fo', 'b', 'ba']\n",
+      "[x.upper() for x in strings if x[0] == 'b']"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 28,
+       "text": [
+        "['BAR', 'BAZ', 'B', 'BA']"
+       ]
+      }
+     ],
+     "prompt_number": 28
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "List comprehensions can be nested"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "list_of_tuples = [(1, 2, 3), (4, 5, 6), (7, 8, 9)]\n",
+      "[x for tup in list_of_tuples for x in tup]"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 29,
+       "text": [
+        "[1, 2, 3, 4, 5, 6, 7, 8, 9]"
+       ]
+      }
+     ],
+     "prompt_number": 29
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## Dict Comprehension"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Create a lookup map of strings and their locations in the list for strings that start with a 'b'"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "{index : val for index, val in enumerate(strings) if val[0] == 'b'}"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 30,
+       "text": [
+        "{1: 'bar', 2: 'baz', 5: 'b', 6: 'ba'}"
+       ]
+      }
+     ],
+     "prompt_number": 30
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## Set Comprehension"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Get the unique lengths of strings that start with a 'b'"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "{len(x) for x in strings if x[0] == 'b'}"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 31,
+       "text": [
+        "{1, 2, 3}"
+       ]
+      }
+     ],
+     "prompt_number": 31
     }
    ],
    "metadata": {}