Bug with save-load sequence. Inverse flattening representation changes between save-load, resulting in a failled equality condition. Also demonstrates the lack of support for a scalar cube.

BUG_save_load_coord_system

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  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Bug with save-load sequence with inverse flattening"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Result of this is that equality condition will fail."
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 40
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import shutil\n",
      "import tempfile\n",
      "\n",
      "\n",
      "class TemporaryDirectory(object):\n",
      "    \"\"\"\n",
      "    Context manager for tempfile.mkdtemp().\n",
      "\n",
      "    This class is available in python +v3.2.\n",
      "\n",
      "    \"\"\"\n",
      "    def __enter__(self):\n",
      "        self.dir_name = tempfile.mkdtemp()\n",
      "        return self.dir_name\n",
      "       \n",
      "    def __exit__(self, exc_type, exc_value, traceback):\n",
      "        shutil.rmtree(self.dir_name)\n",
      "    \n",
      "     \n",
      "TemporaryDirectory = getattr(tempfile, 'TemporaryDirectory',\n",
      "                             TemporaryDirectory)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 10
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import iris\n",
      "\n",
      "\n",
      "cube = iris.cube.Cube([1])\n",
      "airy1830 = iris.coord_systems.GeogCS(semi_major_axis=6377563.396, inverse_flattening=299.3249646)\n",
      "x_coord = iris.coords.DimCoord(1, standard_name='longitude',\n",
      "                               units='degree_east',\n",
      "                               coord_system=airy1830)\n",
      "cube.add_dim_coord(x_coord, 0)\n",
      "x1_coord_system = x_coord.coord_system"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 32
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import os\n",
      "\n",
      "with TemporaryDirectory() as fdir:\n",
      "    fnme = os.path.join(fdir, 'tmp.nc')\n",
      "    iris.save(cube, fnme)\n",
      "    cube2 = iris.load_cube(fnme)\n",
      "    x2_coord_system = cube2.coords()[0].coord_system"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "unknown / (1)                       (longitude: 1)\n",
        "     Dimension coordinates:\n",
        "          longitude                           x\n",
        "     Attributes:\n",
        "          Conventions: CF-1.5\n"
       ]
      }
     ],
     "prompt_number": 30
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "print x1_coord_system == x2_coord_system\n",
      "print x1_coord_system.inverse_flattening, x2_coord_system.inverse_flattening\n",
      "print x1_coord_system.inverse_flattening == x2_coord_system.inverse_flattening"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "False\n",
        "299.3249646 299.3249646\n",
        "False\n"
       ]
      }
     ],
     "prompt_number": 39
    },
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Scalar cube failure save-load sequence failure"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "cube = iris.cube.Cube(1, long_name='scalar_cube')\n",
      "airy1830 = iris.coord_systems.GeogCS(semi_major_axis=6377563.396, inverse_flattening=299.3249646)\n",
      "x_coord = iris.coords.DimCoord(1, standard_name='longitude',\n",
      "                               units='degree_east',\n",
      "                               coord_system=airy1830)\n",
      "cube.add_aux_coord(x_coord, None)\n",
      "x1_coord_system = x_coord.coord_system\n",
      "\n",
      "print cube"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "scalar_cube / (unknown)             (scalar cube)\n",
        "     Scalar coordinates:\n",
        "          longitude: 1 degree_east\n"
       ]
      }
     ],
     "prompt_number": 44
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "with TemporaryDirectory() as fdir:\n",
      "    fnme = os.path.join(fdir, 'tmp.nc')\n",
      "    iris.save(cube, fnme)\n",
      "    cube2 = iris.load_cube(fnme)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "ename": "ConstraintMismatchError",
       "evalue": "no cubes found",
       "output_type": "pyerr",
       "traceback": [
        "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[1;31mConstraintMismatchError\u001b[0m                   Traceback (most recent call last)",
        "\u001b[1;32m<ipython-input-45-18b491f13e36>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[0;32m      2\u001b[0m     \u001b[0mfnme\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0mos\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mpath\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mjoin\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mfdir\u001b[0m\u001b[1;33m,\u001b[0m \u001b[1;34m'tmp.nc'\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      3\u001b[0m     \u001b[0miris\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0msave\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mcube\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mfnme\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 4\u001b[1;33m     \u001b[0mcube2\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0miris\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mload_cube\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mfnme\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
        "\u001b[1;32m/home/h05/cpelley/git/iris/lib/iris/__init__.pyc\u001b[0m in \u001b[0;36mload_cube\u001b[1;34m(uris, constraint, callback)\u001b[0m\n\u001b[0;32m    332\u001b[0m         \u001b[1;32mraise\u001b[0m \u001b[0miris\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mexceptions\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mConstraintMismatchError\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mstr\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0me\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    333\u001b[0m     \u001b[1;32mexcept\u001b[0m \u001b[0mValueError\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m--> 334\u001b[1;33m         \u001b[1;32mraise\u001b[0m \u001b[0miris\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mexceptions\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mConstraintMismatchError\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;34m'no cubes found'\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m    335\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    336\u001b[0m     \u001b[1;32mreturn\u001b[0m \u001b[0mcube\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n",
        "\u001b[1;31mConstraintMismatchError\u001b[0m: no cubes found"
       ]
      }
     ],
     "prompt_number": 45
    }
   ],
   "metadata": {}
  }
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}