decorators.ipynb

{
 "metadata": {
  "name": "Some decorator ideas for dealing with array-order-dependent code"
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "By David Warde-Farley, Oct 25 2012. BSD License all 'round."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import functools\n",
      "\n",
      "def ensure_fortran(*args, **kwargs):\n",
      "    \"\"\"\n",
      "    Modifies attributes of `self` named as positional arguments\n",
      "    to be F-contiguous if they are not already.\n",
      "    \"\"\"\n",
      "    assert len(kwargs) == 0, \"keyword arguments not supported\"\n",
      "    def wrap(method):\n",
      "        @functools.wraps(method)\n",
      "        def wrapped(self, *pargs, **kwargs):\n",
      "            for name in args:\n",
      "                attr = getattr(self, name)\n",
      "                if not attr.flags.fortran:\n",
      "                    setattr(self, name, attr.copy('F'))\n",
      "            return method(self, *pargs, **kwargs)\n",
      "        return wrapped\n",
      "    return wrap"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import numpy as np\n",
      "\n",
      "class Foo(object):\n",
      "    def __init__(self):\n",
      "        self.x = np.empty((2, 2), order='C')\n",
      "        self.y = np.empty((2, 2), order='C')\n",
      "\n",
      "    @ensure_fortran('x', 'y')\n",
      "    def bar(self):\n",
      "        assert self.x.flags.fortran\n",
      "        assert self.x.flags.f_contiguous\n",
      "        assert self.y.flags.fortran\n",
      "        assert self.y.flags.f_contiguous"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 2
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "Foo().bar()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import functools\n",
      "\n",
      "def force_array_order(*args, **deco_kwargs):\n",
      "    \"\"\"A similar decorator capable of enforcing C or F contiguity.\"\"\"\n",
      "    assert len(args) == 0, \"positional arguments not supported\"\n",
      "    def wrap(method):\n",
      "        @functools.wraps(method)\n",
      "        def wrapped(self, *args, **kwargs):\n",
      "            for name, contig in deco_kwargs.iteritems():\n",
      "                attr = getattr(self, name)\n",
      "                contig = contig.lower()\n",
      "                if contig in ('c', 'f'):\n",
      "                    if not getattr(attr.flags, contig + '_contiguous'):\n",
      "                        setattr(self, name, attr.copy(contig.upper()))\n",
      "                else:\n",
      "                    raise ValueError(\"unknown contiguity mode '%s'\" % str(contig))\n",
      "            return method(self, *args, **kwargs)\n",
      "        return wrapped\n",
      "    return wrap"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 4
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "class Bar(object):\n",
      "    def __init__(self):\n",
      "        self.x = np.empty((2, 2), order='F')\n",
      "        self.y = np.empty((2, 2), order='C')\n",
      "    \n",
      "    @force_array_order(x='c', y='f')\n",
      "    def baz(self):\n",
      "        assert self.x.flags.c_contiguous\n",
      "        assert self.y.flags.f_contiguous"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 5
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "Bar().baz()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 6
    }
   ],
   "metadata": {}
  }
 ]
}