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  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# List Comprehension 2\n",
      "\n",
      "- **Author:** [Chris Albon](http://www.chrisalbon.com/), [@ChrisAlbon](https://twitter.com/chrisalbon)\n",
      "- **Date:** -\n",
      "- **Repo:** [Python 3 code snippets for data science](https://github.com/chrisalbon/code_py)\n",
      "- **Note:** Based on http://datasciencelab.wordpress.com/2014/01/08/list-comprehension-in-python/"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## First Letter Of Every Word"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Import the string module"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import string"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 6
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Create a variable that includes all punctuation and adds a blank space\n",
      "\n",
      "string.punctuation is: !\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "punct = string.punctuation + ' '"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 7
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Create a string for all vowels"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "vowels = 'aeiou'"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 8
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Create some text"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "phrase = 'Strictly speaking Python strings are categorized as immutable sequences'"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 9
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Create a variable for the first letter in every word of phase, after split up"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "first_letter = [w[0] for w in phrase.split()]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 10
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Print it out"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "first_letter"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 11,
       "text": [
        "['S', 's', 'P', 's', 'a', 'c', 'a', 'i', 's']"
       ]
      }
     ],
     "prompt_number": 11
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### In the above example here is the breakdown of the list Comprehension\n",
      "\n",
      "- [w[0]             is the output. That is, what we want done.\n",
      "- for w in          is the iterator identifier\n",
      "- phrase.split()]   is the input"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### You can also add a conditional statement"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Create some simulated numbers"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 12
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Create a variable called output that squared every element in numbers variable if it is divisible by 2"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "output = [x**2 for x in numbers if x%2 == 0]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 13
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### View the output"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "output"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 14,
       "text": [
        "[0, 4, 16, 36, 64, 100]"
       ]
      }
     ],
     "prompt_number": 14
    }
   ],
   "metadata": {}
  }
 ]
}