data-science-ipython-notebooks/core/structs.ipynb

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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# Data Structures"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## tuple"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "One dimensional, fixed-length, immutable sequence"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "tup = (1, 2, 3)\n",
      "tup"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 1,
       "text": [
        "(1, 2, 3)"
       ]
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "list_1 = [1, 2, 3]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Convert to a tuple"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "type(tuple(list_1))"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 3,
       "text": [
        "tuple"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Nested tuples"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_tup = ([1, 2, 3], (4, 5))\n",
      "nested_tup"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 4,
       "text": [
        "([1, 2, 3], (4, 5))"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Access by index O(1)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_tup[0]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 5,
       "text": [
        "[1, 2, 3]"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Although tuples are immutable, their contents can contain mutable objects"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_tup[0].append(4)\n",
      "nested_tup[0]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 6,
       "text": [
        "[1, 2, 3, 4]"
       ]
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Concatenate tuples by creating a new tuple and copying objects"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "(1, 3, 2) + (4, 5, 6)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 7,
       "text": [
        "(1, 3, 2, 4, 5, 6)"
       ]
      }
     ],
     "prompt_number": 7
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Multiply copies references to objects (objects themselves are not copied)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "('foo', 'bar') * 2"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 8,
       "text": [
        "('foo', 'bar', 'foo', 'bar')"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Unpack tuples"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "a, b = nested_tup\n",
      "a, b"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 9,
       "text": [
        "([1, 2, 3, 4], (4, 5))"
       ]
      }
     ],
     "prompt_number": 9
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Unpack nested tuples"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "(a, b, c, d), (e, f) = nested_tup\n",
      "a, b, c, d, e, f"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 10,
       "text": [
        "(1, 2, 3, 4, 4, 5)"
       ]
      }
     ],
     "prompt_number": 10
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "A common use of variable unpacking is when iterating over sequences of tuples or lists"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "seq = [( 1, 2, 3), (4, 5, 6), (7, 8, 9)] \n",
      "for a, b, c in seq: \n",
      "    print(a, b, c)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "(1, 2, 3)\n",
        "(4, 5, 6)\n",
        "(7, 8, 9)\n"
       ]
      }
     ],
     "prompt_number": 11
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## list"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "One dimensional, variable-length, mutable sequence"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "list_1 = [1, 2, 3]\n",
      "list_1"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 12,
       "text": [
        "[1, 2, 3]"
       ]
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Convert to a list"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "type(list(tup))"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 13,
       "text": [
        "list"
       ]
      }
     ],
     "prompt_number": 13
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Nested list"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_list = [(1, 2, 3), [4, 5]]\n",
      "nested_list"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 14,
       "text": [
        "[(1, 2, 3), [4, 5]]"
       ]
      }
     ],
     "prompt_number": 14
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Access by index"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_list[1]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 15,
       "text": [
        "[4, 5]"
       ]
      }
     ],
     "prompt_number": 15
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Append an element O(1)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_list.append(6)\n",
      "nested_list"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 16,
       "text": [
        "[(1, 2, 3), [4, 5], 6]"
       ]
      }
     ],
     "prompt_number": 16
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Insert an element at a specific index.  Insert is expensive as it has to shift subsequent elements O(n)."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_list.insert(0, 'start')\n",
      "nested_list"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 17,
       "text": [
        "['start', (1, 2, 3), [4, 5], 6]"
       ]
      }
     ],
     "prompt_number": 17
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Pop removes and returns an element from a specified index.  Pop is expensive as it has to shift subsequent elements O(n).  O(1) if pop is used for the last element"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_list.pop(0)\n",
      "nested_list"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 18,
       "text": [
        "[(1, 2, 3), [4, 5], 6]"
       ]
      }
     ],
     "prompt_number": 18
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Remove locates the first such value and removes it O(n)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_list.remove((1, 2, 3))\n",
      "nested_list"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 19,
       "text": [
        "[[4, 5], 6]"
       ]
      }
     ],
     "prompt_number": 19
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Check if a list contains a value O(n)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "6 in nested_list"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 20,
       "text": [
        "True"
       ]
      }
     ],
     "prompt_number": 20
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Concatenate lists by creating a new list and copying objects"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "[1, 3, 2] + [4, 5, 6]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 21,
       "text": [
        "[1, 3, 2, 4, 5, 6]"
       ]
      }
     ],
     "prompt_number": 21
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Extend a list by appending elements.  Faster than concatenating lists."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nested_list.extend([7, 8, 9])\n",
      "nested_list"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 22,
       "text": [
        "[[4, 5], 6, 7, 8, 9]"
       ]
      }
     ],
     "prompt_number": 22
    }
   ],
   "metadata": {}
  }
 ]
}