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

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  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# Basics"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "* References\n",
      "* Types\n",
      "* Attributes and Methods\n",
      "* Duck Typing Utilities\n",
      "* Duck Typing Utilities Unit Tests\n",
      "* Exceptions"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## References"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "a = [1, 2, 3]\n",
      "b = a\n",
      "a == b"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 1,
       "text": [
        "True"
       ]
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "a is b"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 2,
       "text": [
        "True"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "list() always creates a new list"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "c = list(a)\n",
      "a == c"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 3,
       "text": [
        "True"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "a is c"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 4,
       "text": [
        "False"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Types"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Knowing the type of an object is important, as it's useful to write functions that can handle many types of input."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "type('foo')"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 5,
       "text": [
        "str"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "isinstance() can take a type or tuple"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "isinstance(7, (int, float))"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 6,
       "text": [
        "True"
       ]
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Attributes and Methods"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "List all attributes and methods"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "dir('foo')"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 7,
       "text": [
        "['__add__',\n",
        " '__class__',\n",
        " '__contains__',\n",
        " '__delattr__',\n",
        " '__doc__',\n",
        " '__eq__',\n",
        " '__format__',\n",
        " '__ge__',\n",
        " '__getattribute__',\n",
        " '__getitem__',\n",
        " '__getnewargs__',\n",
        " '__getslice__',\n",
        " '__gt__',\n",
        " '__hash__',\n",
        " '__init__',\n",
        " '__le__',\n",
        " '__len__',\n",
        " '__lt__',\n",
        " '__mod__',\n",
        " '__mul__',\n",
        " '__ne__',\n",
        " '__new__',\n",
        " '__reduce__',\n",
        " '__reduce_ex__',\n",
        " '__repr__',\n",
        " '__rmod__',\n",
        " '__rmul__',\n",
        " '__setattr__',\n",
        " '__sizeof__',\n",
        " '__str__',\n",
        " '__subclasshook__',\n",
        " '_formatter_field_name_split',\n",
        " '_formatter_parser',\n",
        " 'capitalize',\n",
        " 'center',\n",
        " 'count',\n",
        " 'decode',\n",
        " 'encode',\n",
        " 'endswith',\n",
        " 'expandtabs',\n",
        " 'find',\n",
        " 'format',\n",
        " 'index',\n",
        " 'isalnum',\n",
        " 'isalpha',\n",
        " 'isdigit',\n",
        " 'islower',\n",
        " 'isspace',\n",
        " 'istitle',\n",
        " 'isupper',\n",
        " 'join',\n",
        " 'ljust',\n",
        " 'lower',\n",
        " 'lstrip',\n",
        " 'partition',\n",
        " 'replace',\n",
        " 'rfind',\n",
        " 'rindex',\n",
        " 'rjust',\n",
        " 'rpartition',\n",
        " 'rsplit',\n",
        " 'rstrip',\n",
        " 'split',\n",
        " 'splitlines',\n",
        " 'startswith',\n",
        " 'strip',\n",
        " 'swapcase',\n",
        " 'title',\n",
        " 'translate',\n",
        " 'upper',\n",
        " 'zfill']"
       ]
      }
     ],
     "prompt_number": 7
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Access help"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "help(str.upper)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Help on method_descriptor:\n",
        "\n",
        "upper(...)\n",
        "    S.upper() -> string\n",
        "    \n",
        "    Return a copy of the string S converted to uppercase.\n",
        "\n"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Access an attribute or method by name getattr, hasattr, and setattr can be used to write generic, reusable code"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "getattr('foo', 'split')"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 9,
       "text": [
        "<function split>"
       ]
      }
     ],
     "prompt_number": 9
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Duck Typing Utilities"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%%file type_util.py\n",
      "class TypeUtil:\n",
      "\n",
      "    @classmethod\n",
      "    def is_iterable(cls, obj):\n",
      "        \"\"\"Determines if obj is iterable.\n",
      "\n",
      "        Useful when writing functions that can accept multiple types of\n",
      "        input (list, tuple, ndarray, iterator).  Pairs well with\n",
      "        convert_to_list.\n",
      "        \"\"\"\n",
      "        try:\n",
      "            iter(obj)\n",
      "            return True\n",
      "        except TypeError:\n",
      "            return False\n",
      "\n",
      "    @classmethod\n",
      "    def convert_to_list(cls, obj):\n",
      "        \"\"\"Converts obj to a list if it is not a list and it is iterable, \n",
      "        else returns the original obj.\n",
      "        \"\"\"\n",
      "        if not isinstance(obj, list) and cls.is_iterable(obj):\n",
      "            obj = list(obj)\n",
      "        return obj\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Overwriting type_util.py\n"
       ]
      }
     ],
     "prompt_number": 10
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Duck Typing Utilities Unit Tests"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%%file tests/test_type_util.py\n",
      "from nose.tools import assert_equal\n",
      "from pydatasnippets.core.type_util import TypeUtil\n",
      "\n",
      "\n",
      "class TestUtil():\n",
      "\n",
      "    def test_is_iterable(self):\n",
      "        assert_equal(TypeUtil.is_iterable('foo'), True)\n",
      "        assert_equal(TypeUtil.is_iterable(7), False)\n",
      "\n",
      "    def test_convert_to_list(self):\n",
      "        assert_equal(isinstance(TypeUtil.convert_to_list('foo'), list), True)\n",
      "        assert_equal(isinstance(TypeUtil.convert_to_list(7), list), False)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Overwriting tests/test_type_util.py\n"
       ]
      }
     ],
     "prompt_number": 11
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "!nosetests tests/test_type_util.py"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "..\r\n",
        "----------------------------------------------------------------------\r\n",
        "Ran 2 tests in 0.001s\r\n",
        "\r\n",
        "OK\r\n"
       ]
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Exceptions"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def convert_to_float(x):\n",
      "    try:\n",
      "        x = float(x)\n",
      "    except ValueError:\n",
      "        print('Failed')\n",
      "    else: \n",
      "        # Executes only when try succeeds\n",
      "        print('Succeeded')\n",
      "    finally: \n",
      "        # Always executes\n",
      "        print('Completed convert_to_float')\n",
      "        return x"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 13
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "x = convert_to_float('7')\n",
      "x"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Succeeded\n",
        "Completed convert_to_float\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 14,
       "text": [
        "7.0"
       ]
      }
     ],
     "prompt_number": 14
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "x = convert_to_float('a')\n",
      "x"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Failed\n",
        "Completed convert_to_float\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 15,
       "text": [
        "'a'"
       ]
      }
     ],
     "prompt_number": 15
    }
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   "metadata": {}
  }
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