pythonic.ipynb

{
 "metadata": {
  "name": ""
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Swap variables Don't\n",
      "a = 1\n",
      "b = 2\n",
      "print a, b\n",
      "\n",
      "tmp = b\n",
      "b = a\n",
      "a = tmp\n",
      "\n",
      "print a, b"
     ],
     "language": "python",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "1 2\n",
        "2 1\n"
       ]
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Swap variables Do\n",
      "a = 1\n",
      "b = 2\n",
      "print a, b\n",
      "\n",
      "a, b = b, a\n",
      "print a, b"
     ],
     "language": "python",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "1 2\n",
        "2 1\n"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Unpacking tuples Don't\n",
      "person_info = (\"Mary\", 27)\n",
      "\n",
      "name = person_info[0]\n",
      "age = person_info[1]\n",
      "\n",
      "print name\n",
      "print age"
     ],
     "language": "python",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Mary\n",
        "27\n"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Unpacking tuples Do\n",
      "person_info = (\"Mary\", 27)\n",
      "\n",
      "## Do\n",
      "name, age = person_info\n",
      "print name\n",
      "print age"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Mary\n",
        "27\n"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Iteration over incrementing numbers\n",
      "## Don't do\n",
      "for i in [0, 1, 2, 3, 4]:\n",
      "    print i\n",
      "print \"----------------\"\n",
      "\n",
      "## Don't do\n",
      "for i in range(5):\n",
      "    print i\n",
      "print \"----------------\"\n",
      "\n",
      "## Do - in python 3 do range instead\n",
      "for i in xrange(5):\n",
      "    print i"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "0\n",
        "1\n",
        "2\n",
        "3\n",
        "4\n",
        "----------------\n",
        "0\n",
        "1\n",
        "2\n",
        "3\n",
        "4\n",
        "----------------\n",
        "0\n",
        "1\n",
        "2\n",
        "3\n",
        "4\n"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Iteration over list - Don't do\n",
      "colors = ['red', 'green', 'blue', 'yellow']\n",
      "\n",
      "for i in range(len(colors)):\n",
      "    print colors[i]\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "red\n",
        "green\n",
        "blue\n",
        "yellow\n"
       ]
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Iteration over list - Do\n",
      "colors = ['red', 'green', 'blue', 'yellow']\n",
      "\n",
      "for color in colors:\n",
      "    print color"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "red\n",
        "green\n",
        "blue\n",
        "yellow\n"
       ]
      }
     ],
     "prompt_number": 7
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Iteration over list with index - Don't do\n",
      "colors = ['red', 'green', 'blue', 'yellow']\n",
      "\n",
      "for i in range(len(colors)):\n",
      "    print i, '-->', colors[i]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "0 --> red\n",
        "1 --> green\n",
        "2 --> blue\n",
        "3 --> yellow\n"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Iteration over list with index - Do\n",
      "colors = ['red', 'green', 'blue', 'yellow']\n",
      "for i, color in enumerate(colors):\n",
      "    print i, '-->', color"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "0 --> red\n",
        "1 --> green\n",
        "2 --> blue\n",
        "3 --> yellow\n",
        "[(0, 'red'), (1, 'green'), (2, 'blue'), (3, 'yellow')]\n"
       ]
      }
     ],
     "prompt_number": 33
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Constructing list - Don't do\n",
      "kids = [{\"name\": \"peter\", \"age\": 3}, {\"name\": \"leon\", \"age\": 0.3}, {\"name\": \"erwin\", \"age\": 0.2}, {\"name\": \"mirto\", \"age\": 2}]\n",
      "names = []\n",
      "for kid in kids:\n",
      "    names.append(kid[\"name\"])\n",
      "print names"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "['peter', 'leon', 'erwin', 'mirto']\n"
       ]
      }
     ],
     "prompt_number": 10
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Constructing list - Do list comprehension\n",
      "kids = [{\"name\": \"peter\", \"age\": 3}, {\"name\": \"leon\", \"age\": 0.3}, {\"name\": \"erwin\", \"age\": 0.2}, {\"name\": \"mirto\", \"age\": 2}]\n",
      "names = [kid[\"name\"] for kid in kids]\n",
      "print names\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "['peter', 'leon', 'erwin', 'mirto']\n"
       ]
      }
     ],
     "prompt_number": 11
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Constructing list - Don't do\n",
      "kids = [{\"name\": \"peter\", \"age\": 3}, {\"name\": \"leon\", \"age\": 0.3}, {\"name\": \"erwin\", \"age\": 0.2}, {\"name\": \"mirto\", \"age\": 2}]\n",
      "\n",
      "baby_names = []\n",
      "for kid in kids:\n",
      "    if kid[\"age\"] < 1:\n",
      "        baby_names.append(kid[\"name\"])\n",
      "print baby_names"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "['leon', 'erwin']\n"
       ]
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Constructing list - Do list comprehension\n",
      "kids = [{\"name\": \"peter\", \"age\": 3}, {\"name\": \"leon\", \"age\": 0.3}, {\"name\": \"erwin\", \"age\": 0.2}, {\"name\": \"mirto\", \"age\": 2}]\n",
      "\n",
      "baby_names = [kid[\"name\"] for kid in kids if kid[\"age\"] < 1]\n",
      "print baby_names"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "['leon', 'erwin']\n"
       ]
      }
     ],
     "prompt_number": 36
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Get sum of all numbers until 100\n",
      "# Don't do\n",
      "total = 0\n",
      "for num in range(101):\n",
      "    total += num\n",
      "\n",
      "## Do\n",
      "total = sum(range(101))\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 14
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Get sum of all squares of numbers until 100\n",
      "# Don't do\n",
      "total = 0\n",
      "for num in range(101):\n",
      "    total += num**2\n",
      "\n",
      "# Do\n",
      "total = sum([n**2 for n in range(101)])\n",
      "\n",
      "# Even Better - Generators\n",
      "total = sum(n**2 for n in range(101))"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 15
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Concatenate strings from list - Don't\n",
      "names = [\"Betty\", \"Patty\", \"Johanna\", \"Ivana\", \"Luminitsa\"]\n",
      "\n",
      "s = names[0]\n",
      "for name in names[1:]:\n",
      "    s += ', ' + name\n",
      "print s"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Betty, Patty, Johanna, Ivana, Luminitsa\n"
       ]
      }
     ],
     "prompt_number": 16
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Concatenate strings from list - Do\n",
      "names = [\"Betty\", \"Patty\", \"Johanna\", \"Ivana\", \"Luminitsa\"]\n",
      "\n",
      "s = ', '.join(names)\n",
      "print s"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Betty, Patty, Johanna, Ivana, Luminitsa\n"
       ]
      }
     ],
     "prompt_number": 17
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Sorting - alphabetically\n",
      "names = [\"Betty\", \"Patty\", \"Johanna\", \"Ivana\", \"Luminitsa\"]\n",
      "\n",
      "for name in sorted(names):\n",
      "    print name"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Betty\n",
        "Ivana\n",
        "Johanna\n",
        "Luminitsa\n",
        "Patty\n"
       ]
      }
     ],
     "prompt_number": 18
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "## Sorting descending\n",
      "names = [\"Betty\", \"Patty\", \"Johanna\", \"Ivana\", \"Luminitsa\"]\n",
      "\n",
      "for name in sorted(names, reverse=True):\n",
      "    print name"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Patty\n",
        "Luminitsa\n",
        "Johanna\n",
        "Ivana\n",
        "Betty\n"
       ]
      }
     ],
     "prompt_number": 19
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Sorting by string length\n",
      "names = [\"Betty\", \"Patty\", \"Johanna\", \"Ivana\", \"Luminitsa\"]\n",
      "for name in sorted(names, key=len):\n",
      "    print name\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Betty\n",
        "Patty\n",
        "Ivana\n",
        "Johanna\n",
        "Luminitsa\n"
       ]
      }
     ],
     "prompt_number": 20
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Sorting by number of a\n",
      "def count_a(word):\n",
      "    return sum(1 for ch in word if ch == 'a')\n",
      "\n",
      "for name in sorted(names, key=count_a):\n",
      "    print name"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Betty\n",
        "Patty\n",
        "Luminitsa\n",
        "Johanna\n",
        "Ivana\n"
       ]
      }
     ],
     "prompt_number": 21
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Sorting by second tuple element\n",
      "names = [(\"Mary\", 27), (\"John\", 28), \n",
      "        (\"Peter\", 17), (\"Helen\", 13)]\n",
      "\n",
      "from operator import itemgetter\n",
      "\n",
      "for name, age in sorted(names, key=itemgetter(1)):\n",
      "    print name\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Helen\n",
        "Peter\n",
        "Mary\n",
        "John\n"
       ]
      }
     ],
     "prompt_number": 22
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Counting with dictionaries -  Don't do\n",
      "colors = ['red', 'green', 'red', 'blue', 'green', 'red']\n",
      "\n",
      "d = {}\n",
      "for color in colors:\n",
      "    if color not in d:\n",
      "        d[color] = 0\n",
      "    d[color] += 1\n",
      "print d\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "{'blue': 1, 'green': 2, 'red': 3}\n"
       ]
      }
     ],
     "prompt_number": 23
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Counting with dictionaries -  Do\n",
      "colors = ['red', 'green', 'red', 'blue', 'green', 'red']\n",
      "d = {}\n",
      "for color in colors:\n",
      "    d[color] = d.get(color, 0) + 1\n",
      "print d"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "{'blue': 1, 'green': 2, 'red': 3}\n"
       ]
      }
     ],
     "prompt_number": 24
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Counting with dictionaries -  Do alterrnative\n",
      "colors = ['red', 'green', 'red', 'blue', 'green', 'red']\n",
      "from collections import defaultdict\n",
      "d = defaultdict(int)\n",
      "for color in colors:\n",
      "    d[color] += 1\n",
      "print d"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "defaultdict(<type 'int'>, {'blue': 1, 'green': 2, 'red': 3})\n"
       ]
      }
     ],
     "prompt_number": 25
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Grouping with dictionaries - Don't do\n",
      "colors = ['gray', 'black', 'blue', 'green', 'red']\n",
      "\n",
      "d = {}\n",
      "for color in colors:\n",
      "    first_char = color[0]\n",
      "    if first_char not in d:\n",
      "        d[first_char] = []\n",
      "    d[first_char].append(color)\n",
      "print d\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "{'r': ['red'], 'b': ['black', 'blue'], 'g': ['gray', 'green']}\n"
       ]
      }
     ],
     "prompt_number": 26
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Grouping with dictionaries - Do\n",
      "from collections import defaultdict\n",
      "d = defaultdict(list)\n",
      "for color in colors:\n",
      "    first_char = color[0]\n",
      "    d[first_char].append(color)\n",
      "print d    \n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "defaultdict(<type 'list'>, {'r': ['red'], 'b': ['black', 'blue'], 'g': ['gray', 'green']})\n"
       ]
      }
     ],
     "prompt_number": 27
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Looping over dictionaries keys\n",
      "city_music = {\"berlin\": \"techno\", \n",
      "              \"seville\": \"flamenco\", \n",
      "              \"new york\": \"jazz\"}\n",
      "\n",
      "for city in city_music:\n",
      "    print city\n",
      "    \n",
      "    \n",
      "europe = ('berlin', 'seville', 'madrid', 'paris',)\n",
      "\n",
      "# to change the dictionary while looping - Do\n",
      "for city in city_music.keys():\n",
      "    if city not in europe:\n",
      "        del city_music[city]\n",
      "print city_music        \n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "berlin\n",
        "new york\n",
        "seville\n",
        "{'berlin': 'techno', 'seville': 'flamenco'}\n"
       ]
      }
     ],
     "prompt_number": 28
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Looping over dictionaries keys and values\n",
      "city_music = {\"berlin\": \"techno\", \n",
      "              \"seville\": \"flamenco\", \n",
      "              \"new york\": \"jazz\"}\n",
      "\n",
      "for city in city_music:\n",
      "    print city, 'listens to', city_music[city] "
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "berlin listens to techno\n",
        "new york listens to jazz\n",
        "seville listens to flamenco\n"
       ]
      }
     ],
     "prompt_number": 29
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# Looping over dictionaries keys and values    \n",
      "# more readable\n",
      "for city, music in city_music.items():\n",
      "    print city, 'listens to', music "
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "berlin listens to techno\n",
        "new york listens to jazz\n",
        "seville listens to flamenco\n"
       ]
      }
     ],
     "prompt_number": 30
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Looping over dictionaries keys and values    \n",
      "# more readable and faster\n",
      "for city, music in city_music.iteritems():\n",
      "    print city, 'listens to', music"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "berlin listens to techno\n",
        "new york listens to jazz\n",
        "seville listens to flamenco\n"
       ]
      }
     ],
     "prompt_number": 31
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 31
    }
   ],
   "metadata": {}
  }
 ]
}