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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# Decorators in Python\n",
      "> Shrayas (@shrayasr)"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "---"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "#Recap on Functions"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## 1. Functions can be defined inside functions"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def say_something(thought):\n",
      "    \n",
      "    def _thought_makes_sense(thought):\n",
      "        return True\n",
      "    \n",
      "    if _thought_makes_sense(thought):\n",
      "        return thought\n",
      "    \n",
      "print say_something(\"That person stinks!\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "That person stinks!\n"
       ]
      }
     ],
     "prompt_number": 26
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## 2. Functions are Lexically scoped"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def say_something(thought):\n",
      "    \n",
      "    def _thought_makes_sense():\n",
      "        print \"HMMM \\\"\"+thought+\"\\\"... I Wonder...\"\n",
      "        return True\n",
      "    \n",
      "    if _thought_makes_sense():\n",
      "        return thought\n",
      "    \n",
      "print say_something(\"That person stinks!\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "HMMM \"That person stinks!\"... I Wonder...\n",
        "That person stinks!\n"
       ]
      }
     ],
     "prompt_number": 27
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## 3. Functions can be passed as arguments to other Functions"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def say_something(thought, tone=None):\n",
      "    return tone(thought)\n",
      "\n",
      "def yell(thought):\n",
      "    return thought.upper()\n",
      "\n",
      "def whisper(thought):\n",
      "    return \"Shhh... \" + thought.lower()\n",
      "\n",
      "print say_something(\"where are you babu?\", tone=yell)\n",
      "print say_something(\"Lets go get an ice cream!\", tone=whisper)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "WHERE ARE YOU BABU?\n",
        "Shhh... lets go get an ice cream!\n"
       ]
      }
     ],
     "prompt_number": 28
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## 4. Functions can be returned from functions"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def mood_maker(mood):\n",
      "    \n",
      "    def happy(thought):\n",
      "        return \"^_^ \" + thought + \" ^_^\"\n",
      "    \n",
      "    def sad(thought):\n",
      "        return thought + \" ... :'( sniff\"\n",
      "    \n",
      "    moods = {\n",
      "        \"HAPPY\": happy,\n",
      "        \"SAD\": sad\n",
      "    }\n",
      "    \n",
      "    return moods[mood.upper()]\n",
      "\n",
      "say_happily = mood_maker(\"happy\")\n",
      "print say_happily(\"Hello!\")\n",
      "\n",
      "say_sadly = mood_maker(\"sad\")\n",
      "print say_sadly(\"I lost my favourite pen!\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "^_^ Hello! ^_^\n",
        "I lost my favourite pen! ... :'( sniff\n"
       ]
      }
     ],
     "prompt_number": 29
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "---"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "#Back to business"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Lets add some masala to a function!"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def masala_adder(func):\n",
      "    \n",
      "    def masalad_function():\n",
      "        return \"^#!^^@) [\" + func() + \"] !@&$**^&$\"\n",
      "        \n",
      "    return masalad_function\n",
      "\n",
      "def say_hi():\n",
      "    return \"Hii\"\n",
      "   \n",
      "print say_hi()\n",
      "masala_say_hi = masala_adder(say_hi)\n",
      "print masala_say_hi()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Hii\n",
        "^#!^^@) [Hii] !@&$**^&$\n"
       ]
      }
     ],
     "prompt_number": 30
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Masala, Decorators style!"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "@masala_adder\n",
      "def say_hello():\n",
      "    return \"Hello\"\n",
      "\n",
      "say_hello()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 31,
       "text": [
        "'^#!^^@) [Hello] !@&$**^&$'"
       ]
      }
     ],
     "prompt_number": 31
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Wait, what?"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "say_hello = masala_adder(say_hello)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 32
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      ">Decorators are just syntactic sugar on a function that takes a function and returns a replacement function\n",
      "\n",
      "    A.K.A\n",
      "\n",
      "> Wrappers"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Define decorator here\n",
      "def decorator(func):\n",
      "    \n",
      "    def new_func():\n",
      "        print \"before\"\n",
      "        func()\n",
      "        print \"after\"\n",
      "    \n",
      "    return new_func\n",
      "\n",
      "@decorator\n",
      "def say_hello():\n",
      "    print \"Hello!\"\n",
      "    \n",
      "say_hello()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "before\n",
        "Hello!\n",
        "after\n"
       ]
      }
     ],
     "prompt_number": 33
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Lets make some owls!"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def ears(func):    \n",
      "    def ears_wrapper():\n",
      "        owl_string = \" /\\\\_/\\\\\\n\"\n",
      "        owl_string += func()\n",
      "        return owl_string\n",
      "    \n",
      "    return ears_wrapper\n",
      "\n",
      "def eyes(func):    \n",
      "    def eyes_wrapper():\n",
      "        owl_string = \" (O.O) \\n\"\n",
      "        owl_string += func()\n",
      "        return owl_string\n",
      "    \n",
      "    return eyes_wrapper\n",
      "\n",
      "def body(func):    \n",
      "    def body_wrapper():\n",
      "        owl_string = \" (= =)\\n\"\n",
      "        owl_string += func()\n",
      "        return owl_string\n",
      "    \n",
      "    return body_wrapper\n",
      "\n",
      "def legs(func):    \n",
      "    def legs_wrapper():\n",
      "        owl_string = \"  ^^^\\n\"\n",
      "        owl_string += func()\n",
      "        return owl_string\n",
      "    \n",
      "    return legs_wrapper\n",
      "\n",
      "@ears\n",
      "@eyes\n",
      "@body\n",
      "@legs\n",
      "def owl():\n",
      "    return \"hoot hoot\"\n",
      "\n",
      "print owl()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        " /\\_/\\\n",
        " (O.O) \n",
        " (= =)\n",
        "  ^^^\n",
        "hoot hoot\n"
       ]
      }
     ],
     "prompt_number": 34
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "owl = ears(eyes(body(legs(owl))))"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 35
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Arguments to decorated functions"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def decorator(func):\n",
      "    def new_func(arg1, arg2):\n",
      "        print \"I R HAZ ARGZ! [%s, %s]\" % (arg1, arg2)\n",
      "        return func(arg1, arg2)\n",
      "    return new_func\n",
      "\n",
      "@decorator\n",
      "def sum_of_squares(num1, num2):\n",
      "    print num1*num1 + num2*num2\n",
      "    \n",
      "sum_of_squares(1,2)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "I R HAZ ARGZ! [1, 2]\n",
        "5\n"
       ]
      }
     ],
     "prompt_number": 36
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def logger(func):\n",
      "    def decorated_function(*args, **kwargs):\n",
      "        print \"[INFO][Arguments]\", args, kwargs\n",
      "        return func(*args, **kwargs)\n",
      "    return decorated_function\n",
      "\n",
      "@logger\n",
      "def sum_of_squares(num1, num2):\n",
      "    print num1*num1 + num2*num2\n",
      "    \n",
      "@logger\n",
      "def csv_reader(file_path, record_delimiter=\",\", line_delimiter=\"\\n\"):\n",
      "    print \"reading csv\"\n",
      "    \n",
      "sum_of_squares(1,2)\n",
      "csv_reader(\"/etc/init.d\", record_delimiter=\";\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "[INFO][Arguments] (1, 2) {}\n",
        "5\n",
        "[INFO][Arguments] ('/etc/init.d',) {'record_delimiter': ';'}\n",
        "reading csv\n"
       ]
      }
     ],
     "prompt_number": 37
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Exercise: Lets use decorators!"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "> Let us write a small cache!"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "_cache = {}\n",
      "\n",
      "\"\"\"\n",
      "1_2 => 3\n",
      "\"\"\"\n",
      "\n",
      "def cache(func):\n",
      "    \n",
      "    def new_func(*args, **kwargs):\n",
      "        \n",
      "        key_str = \"\"\n",
      "        for arg in args:\n",
      "            key_str += str(arg) + \"_\"\n",
      "        key_str = key_str[:-1]\n",
      "        \n",
      "        val = _cache.get(key_str)\n",
      "        if not val:\n",
      "            val = func(*args)\n",
      "            _cache[key_str] = val\n",
      "        return val\n",
      "    \n",
      "    return new_func"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 38
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import time\n",
      "\n",
      "@cache\n",
      "def add_2_nos(a,b):\n",
      "    time.sleep(2)\n",
      "    return a+b"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 39
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "add_2_nos(1,2)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 40,
       "text": [
        "3"
       ]
      }
     ],
     "prompt_number": 40
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "add_2_nos(1,2)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 41,
       "text": [
        "3"
       ]
      }
     ],
     "prompt_number": 41
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "add_2_nos(10,20)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 42,
       "text": [
        "30"
       ]
      }
     ],
     "prompt_number": 42
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "add_2_nos(10,20)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 43,
       "text": [
        "30"
       ]
      }
     ],
     "prompt_number": 43
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "_cache"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 44,
       "text": [
        "{'10_20': 30, '1_2': 3}"
       ]
      }
     ],
     "prompt_number": 44
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "---"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# Fin."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "---"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "![boom](./blown.gif)"
     ]
    }
   ],
   "metadata": {}
  }
 ]
}