Sorting Python Dictionaries

gistfile1.txt

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   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "<center><h1>Sorting Python Dictionary Examples</h1></center>"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "<h3>I know of 3 different ways to sort a dictionary:</h3>\n",
      "\n",
      "* using sort() method with lambda function (if I remember correctly, this is slowest)\n",
      "* using sort() method using operator.itemgetter\n",
      "* using an OrderedDict from collections.OrderedDict"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "mydict = {'b':4,'a':2,'d':1,'c':3}"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "<h2>Using sort() using lambda function:</h2>\n",
      "\n",
      "---\n",
      "<h4>Sort by values:</h4>"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "my_list_of_tuples = sorted(mydict.items(), key=lambda x: x[1])\n",
      "my_list_of_tuples"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 30,
       "text": [
        "[('d', 1), ('a', 2), ('c', 3), ('b', 4)]"
       ]
      }
     ],
     "prompt_number": 30
    },
    {
     "cell_type": "heading",
     "level": 4,
     "metadata": {},
     "source": [
      "Sort by keys:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "my_list_of_tuples = sorted(mydict.items(), key=lambda x: x[0])\n",
      "my_list_of_tuples"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 31,
       "text": [
        "[('a', 2), ('b', 4), ('c', 3), ('d', 1)]"
       ]
      }
     ],
     "prompt_number": 31
    },
    {
     "cell_type": "heading",
     "level": 4,
     "metadata": {},
     "source": [
      "NOTE: In all 3 methods, you can use the \"reverse\" parameter to sort in descending order:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "my_list_of_tuples = sorted(mydict.items(), key=lambda x: x[1], reverse=True)\n",
      "my_list_of_tuples"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 33,
       "text": [
        "[('b', 4), ('c', 3), ('a', 2), ('d', 1)]"
       ]
      }
     ],
     "prompt_number": 33
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "<h2>Using sort() using operator.itemgetter:</h2>\n",
      "\n",
      "---\n",
      "<h4>Sorting by values</h4>"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "from operator import itemgetter\n",
      "# Sort by value\n",
      "sorted(mydict.items(), key=itemgetter(1))"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 28,
       "text": [
        "[('d', 1), ('a', 2), ('c', 3), ('b', 4)]"
       ]
      }
     ],
     "prompt_number": 28
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "<h4>Sorting by keys</h4>"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Sort by key\n",
      "sorted(mydict.items(), key=itemgetter(0))"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 27,
       "text": [
        "[('a', 2), ('b', 4), ('c', 3), ('d', 1)]"
       ]
      }
     ],
     "prompt_number": 27
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "<h2>Using OrderedDict from collections.OrderedDict:</h2>\n",
      "\n",
      "---\n",
      "<h4>Sorting by values</h4>"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "from collections import OrderedDict\n",
      "\n",
      "d = {'banana': 3, 'apple':4, 'pear': 1, 'orange': 2}\n",
      "OD = OrderedDict(sorted(d.items(), key=lambda t: t[1]))\n",
      "OD"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 35,
       "text": [
        "OrderedDict([('pear', 1), ('orange', 2), ('banana', 3), ('apple', 4)])"
       ]
      }
     ],
     "prompt_number": 35
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "<h4>Sorting by keys</h4>"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "OD = OrderedDict(sorted(d.items(), key=lambda t: t[0]))\n",
      "OD"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 36,
       "text": [
        "OrderedDict([('apple', 4), ('banana', 3), ('orange', 2), ('pear', 1)])"
       ]
      }
     ],
     "prompt_number": 36
    },
    {
     "cell_type": "heading",
     "level": 3,
     "metadata": {},
     "source": [
      "BONUS: Prettyfied way of printing your Python dictionary:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "for key in OD.keys():\n",
      "    print(\"OD[\"+key+\"]:\",OD[key])"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "OD[apple]: 4\n",
        "OD[banana]: 3\n",
        "OD[orange]: 2\n",
        "OD[pear]: 1\n"
       ]
      }
     ],
     "prompt_number": 37
    }
   ],
   "metadata": {}
  }
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