Notes from Advanced Python Workshop.

2 - Functional Programming (Advanced Python Workshop).ipynb

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  "name": "2 - Functional Programming (Advanced Python Workshop)"
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   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# Functional Programming"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Variable arguments and Keyword arguments"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "max(1, 2, 3, 4)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "pyout",
       "prompt_number": 3,
       "text": [
        "4"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "dict(a=1, b=2)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "pyout",
       "prompt_number": 4,
       "text": [
        "{'a': 1, 'b': 2}"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def add(*args): \n",
      "    return sum(args)\n",
      "\n",
      "print add(1, 2, 3, 4)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "10\n"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def mydict(**kwargs):\n",
      "    return kwargs\n",
      "\n",
      "print mydict(a=1, b=2)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "{'a': 1, 'b': 2}\n"
       ]
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def render_tag(tagname, **attrs):\n",
      "    pairs = [\"%s=%s\" % (k,v) for k, v in attrs.items()]\n",
      "    return \"<%s %s/>\" % (tagname, \" \".join(pairs))\n",
      "\n",
      "render_tag(\"input\", type=\"text\", name=\"x\", id=\"x\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "pyout",
       "prompt_number": 10,
       "text": [
        "'<input type=text name=x id=x/>'"
       ]
      }
     ],
     "prompt_number": 10
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "numbers = [1, 2, 3, 4]\n",
      "print add(*numbers)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "10\n"
       ]
      }
     ],
     "prompt_number": 11
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "**Problem:** Write a function `call_func(f, *args, **kwargs)`, that calls the given function f with args and kwargs.\n",
      "\n",
      "    def square(x): \n",
      "        return x*x\n",
      "    print call_func(square, 2)\n",
      "    print call_func(square, x=2)\n",
      "\n",
      "    def add(a, b): \n",
      "        return a + b\n",
      "    print call_func(add, 2, 3)\n",
      "\n",
      "    print call_func(max, 2, 3, 4, 5, 6, 7)\n",
      "    print call_func(dict, a=1, b=2, c=3)"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def add(a, b): return a+b\n",
      "args=[1]\n",
      "kwargs={\"b\": 2}\n",
      "\n",
      "print add(*args, **kwargs)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "3\n"
       ]
      }
     ],
     "prompt_number": 14
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def call_fun(f, *args, **kwargs):\n",
      "    return f(*args, **kwargs)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 15
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "## Back to Decorators "
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import time\n",
      "def timeit(f):\n",
      "    def g():\n",
      "        t0 = time.time()\n",
      "        value = f()\n",
      "        t1 = time.time()\n",
      "        print \"took %f seconds\" % (t1-t0)\n",
      "        return value\n",
      "    return g\n",
      "\n",
      "def timepass():\n",
      "    for i in range(10000):\n",
      "        for j in range(1000):\n",
      "            x = i*j\n",
      "    return 0\n",
      "\n",
      "def timepass2(n):\n",
      "    for i in range(n):\n",
      "        for j in range(1000):\n",
      "            x = i*j\n",
      "    return 0\n",
      "\n",
      "\n",
      "timepass = timeit(timepass)\n",
      "print timepass()\n",
      "\n",
      "import urllib\n",
      "@timeit\n",
      "def wget(url):\n",
      "    return urllib.urlopen(url).read()\n",
      "\n",
      "x = wget(\"http://python.org\")\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "ename": "TypeError",
       "evalue": "g() takes no arguments (1 given)",
       "output_type": "pyerr",
       "traceback": [
        "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
        "\u001b[0;32m<ipython-input-21-868cc2b3e2d9>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m     30\u001b[0m     \u001b[0;32mreturn\u001b[0m \u001b[0murllib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0murlopen\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0murl\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mread\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     31\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 32\u001b[0;31m \u001b[0mx\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mwget\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"http://python.org\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
        "\u001b[0;31mTypeError\u001b[0m: g() takes no arguments (1 given)"
       ]
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "took 0.772692 seconds\n",
        "0\n"
       ]
      }
     ],
     "prompt_number": 21
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "**Problem:** Write a decorator `vectorize`, that takes a function working on single value and make it work on a list.\n",
      "\n",
      "    @vectorize\n",
      "    def square(x):\n",
      "        return x*x\n",
      "\n",
      "    print square([1, 2, 3, 4]) # should print [1, 4, 9, 16]"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Example: Web Framework"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%%file bicycle.py\n",
      "mapping = []\n",
      "before_hooks = []\n",
      "\n",
      "def request(url):\n",
      "    for path, func in mapping:\n",
      "        if path == url:\n",
      "            for h in before_hooks:\n",
      "                h(url)\n",
      "            return func()\n",
      "        \n",
      "    return \"404 - Not Found\"\n",
      "    \n",
      "def route(path):\n",
      "    def decorator(f):\n",
      "        mapping.append((path, f))\n",
      "        return f\n",
      "    return decorator\n",
      "\n",
      "def before_request(f):\n",
      "    before_hooks.append(f)\n",
      "    return f"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Overwriting bicycle.py\n"
       ]
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "from bicycle import route, request, before_request\n",
      "import time\n",
      "\n",
      "@route(\"/hello\")\n",
      "def hello():\n",
      "    return \"Hello, world\"\n",
      "\n",
      "@route(\"/bye\")\n",
      "def bye():\n",
      "    return \"Goodbye\"\n",
      "\n",
      "@before_request\n",
      "def log(url):\n",
      "    print time.asctime(), url\n",
      "\n",
      "if __name__ == \"__main__\":\n",
      "    print \"MAIN\"\n",
      "    print request(\"/hello\") # should print \"Hello, world\"\n",
      "    print request(\"/bye\")\n",
      "    print request(\"/foo\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "MAIN\n",
        "Sat May 25 10:53:05 2013 /hello\n",
        "Hello, world\n",
        "Sat May 25 10:53:05 2013 /bye\n",
        "Goodbye\n",
        "404 - Not Found\n"
       ]
      }
     ],
     "prompt_number": 8
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### Example: writing command line apps using decorators"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%%file command0.py\n",
      "def command(f):\n",
      "    def g(filenames, **kw):\n",
      "        lines = readfiles(filenames)\n",
      "        #lines = (outline for line in lines \n",
      "        #                 for outline in f(line, **kw))\n",
      "        lines = generate_output(f, lines, **kwargs)\n",
      "        printlines(lines)\n",
      "    return g\n",
      "\n",
      "def generate_output(f, lines, **kwargs):\n",
      "    for line in lines:\n",
      "        for outline in f(line, **kwargs):\n",
      "            yield outline\n",
      "\n",
      "def readfiles(filenames):\n",
      "    for f in filenames:\n",
      "        for line in open(f):\n",
      "            yield line\n",
      "\n",
      "def printlines(lines):\n",
      "    for line in lines:\n",
      "        print line.strip(\"\\n\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Overwriting command0.py\n"
       ]
      }
     ],
     "prompt_number": 44
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%%file uppercase.py\n",
      "from command0 import command\n",
      "\n",
      "@command\n",
      "def uppercase(line):\n",
      "    yield line.upper()\n",
      "\n",
      "if __name__ == \"__main__\":\n",
      "    import sys\n",
      "    uppercase(sys.argv[1:])"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Overwriting uppercase.py\n"
       ]
      }
     ],
     "prompt_number": 36
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "!python uppercase.py uppercase.py"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "FROM COMMAND0 IMPORT COMMAND\r\n",
        "\r\n",
        "@COMMAND\r\n",
        "DEF UPPERCASE(LINE):\r\n",
        "    YIELD LINE.UPPER()\r\n",
        "\r\n",
        "IF __NAME__ == \"__MAIN__\":\r\n",
        "    IMPORT SYS\r\n",
        "    UPPERCASE(SYS.ARGV[1:])\r\n"
       ]
      }
     ],
     "prompt_number": 37
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%%file grep.py\n",
      "from command0 import command\n",
      "\n",
      "@command\n",
      "def grep(line, pattern):\n",
      "    if pattern in line:\n",
      "        yield line\n",
      "        \n",
      "if __name__ == \"__main__\":\n",
      "    import sys\n",
      "    pattern = sys.argv[1]\n",
      "    filenames = sys.argv[2:]\n",
      "    grep(filenames, pattern=pattern)\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Overwriting grep.py\n"
       ]
      }
     ],
     "prompt_number": 38
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "!python grep.py def grep.py"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "def grep(line, pattern):\r\n"
       ]
      }
     ],
     "prompt_number": 39
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%%file twice.py\n",
      "from command0 import command\n",
      "\n",
      "@command\n",
      "def twice(line):\n",
      "    yield line\n",
      "    yield line\n",
      "    \n",
      "if __name__ == \"__main__\":\n",
      "    import sys\n",
      "    twice(sys.argv[1:])"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Overwriting twice.py\n"
       ]
      }
     ],
     "prompt_number": 42
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "!python twice.py twice.py"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "from command0 import command\r\n",
        "from command0 import command\r\n",
        "\r\n",
        "\r\n",
        "@command\r\n",
        "@command\r\n",
        "def twice(line):\r\n",
        "def twice(line):\r\n",
        "    yield line\r\n",
        "    yield line\r\n",
        "    yield line\r\n",
        "    yield line\r\n",
        "    \r\n",
        "    \r\n",
        "if __name__ == \"__main__\":\r\n",
        "if __name__ == \"__main__\":\r\n",
        "    import sys\r\n",
        "    import sys\r\n",
        "    twice(sys.argv[1:])\r\n",
        "    twice(sys.argv[1:])\r\n"
       ]
      }
     ],
     "prompt_number": 43
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "### `exec` and `eval`"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "code = \"x = 1\"\n",
      "exec(code)\n",
      "print x"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "1\n"
       ]
      }
     ],
     "prompt_number": 45
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "eval(\"1 + 2\")"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "pyout",
       "prompt_number": 46,
       "text": [
        "3"
       ]
      }
     ],
     "prompt_number": 46
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "env = {\"x\": 2}\n",
      "eval(\"x + 2\", env)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "pyout",
       "prompt_number": 47,
       "text": [
        "4"
       ]
      }
     ],
     "prompt_number": 47
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
 ]
}