getting values from expressions in keras

july_10_example.ipynb

{
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      "metadata": {
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      "cell_type": "code",
      "source": "import keras.backend as K\nimport numpy as np",
      "execution_count": 1,
      "outputs": [
        {
          "output_type": "stream",
          "text": "Using Theano backend.\nUsing gpu device 0: GeForce GTX 980 (CNMeM is disabled, cuDNN 5004)\n",
          "name": "stderr"
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      "cell_type": "code",
      "source": "## this work because x is a variable\nx = K.variable(np.zeros(5,))\nK.get_value(x)",
      "execution_count": 2,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": "array([ 0.,  0.,  0.,  0.,  0.], dtype=float32)"
          },
          "metadata": {},
          "execution_count": 2
        }
      ]
    },
    {
      "metadata": {
        "trusted": true,
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      },
      "cell_type": "code",
      "source": "## this fails because y is an expression\ny = x + 5\nK.get_value(y)",
      "execution_count": 3,
      "outputs": [
        {
          "output_type": "error",
          "ename": "Exception",
          "evalue": "'get_value() can only be called on a variable. If you have an expression instead, use eval().",
          "traceback": [
            "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
            "\u001b[1;31mException\u001b[0m                                 Traceback (most recent call last)",
            "\u001b[1;32m<ipython-input-3-9d401c25f7f5>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[0;32m      1\u001b[0m \u001b[1;31m## this fails because y is an expression\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      2\u001b[0m \u001b[0my\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0mx\u001b[0m \u001b[1;33m+\u001b[0m \u001b[1;36m5\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 3\u001b[1;33m \u001b[0mK\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mget_value\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0my\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
            "\u001b[1;32m/home/cogniton/research/code/keras/keras/backend/theano_backend.py\u001b[0m in \u001b[0;36mget_value\u001b[1;34m(x)\u001b[0m\n\u001b[0;32m    546\u001b[0m     \u001b[1;32mif\u001b[0m \u001b[1;32mnot\u001b[0m \u001b[0mhasattr\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mx\u001b[0m\u001b[1;33m,\u001b[0m \u001b[1;34m'get_value'\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    547\u001b[0m         raise Exception(\"'get_value() can only be called on a variable. \" +\n\u001b[1;32m--> 548\u001b[1;33m                         \"If you have an expression instead, use eval().\")\n\u001b[0m\u001b[0;32m    549\u001b[0m     \u001b[1;32mreturn\u001b[0m \u001b[0mx\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mget_value\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    550\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n",
            "\u001b[1;31mException\u001b[0m: 'get_value() can only be called on a variable. If you have an expression instead, use eval()."
          ]
        }
      ]
    },
    {
      "metadata": {
        "trusted": true,
        "collapsed": false
      },
      "cell_type": "code",
      "source": "## this will also fail. \ny = K.variable(np.zeros(5,))\nK.set_value(y, x+5)\nK.get_value(y)",
      "execution_count": 4,
      "outputs": [
        {
          "output_type": "error",
          "ename": "ValueError",
          "evalue": "setting an array element with a sequence.",
          "traceback": [
            "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
            "\u001b[1;31mValueError\u001b[0m                                Traceback (most recent call last)",
            "\u001b[1;32m<ipython-input-4-fca89c8203fe>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[0;32m      1\u001b[0m \u001b[1;31m## this will also fail.\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      2\u001b[0m \u001b[0my\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0mK\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mvariable\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mnp\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mzeros\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;36m5\u001b[0m\u001b[1;33m,\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 3\u001b[1;33m \u001b[0mK\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mset_value\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0my\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mx\u001b[0m\u001b[1;33m+\u001b[0m\u001b[1;36m5\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m      4\u001b[0m \u001b[0mK\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mget_value\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0my\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n",
            "\u001b[1;32m/home/cogniton/research/code/keras/keras/backend/theano_backend.py\u001b[0m in \u001b[0;36mset_value\u001b[1;34m(x, value)\u001b[0m\n\u001b[0;32m    558\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    559\u001b[0m \u001b[1;32mdef\u001b[0m \u001b[0mset_value\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mx\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m--> 560\u001b[1;33m     \u001b[0mx\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mset_value\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mnp\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0masarray\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mdtype\u001b[0m\u001b[1;33m=\u001b[0m\u001b[0mx\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mdtype\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m    561\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    562\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n",
            "\u001b[1;32m/home/cogniton/anaconda/envs/py3k/lib/python3.5/site-packages/numpy/core/numeric.py\u001b[0m in \u001b[0;36masarray\u001b[1;34m(a, dtype, order)\u001b[0m\n\u001b[0;32m    480\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    481\u001b[0m     \"\"\"\n\u001b[1;32m--> 482\u001b[1;33m     \u001b[1;32mreturn\u001b[0m \u001b[0marray\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0ma\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mdtype\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mcopy\u001b[0m\u001b[1;33m=\u001b[0m\u001b[1;32mFalse\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0morder\u001b[0m\u001b[1;33m=\u001b[0m\u001b[0morder\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m    483\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    484\u001b[0m \u001b[1;32mdef\u001b[0m \u001b[0masanyarray\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0ma\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mdtype\u001b[0m\u001b[1;33m=\u001b[0m\u001b[1;32mNone\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0morder\u001b[0m\u001b[1;33m=\u001b[0m\u001b[1;32mNone\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n",
            "\u001b[1;31mValueError\u001b[0m: setting an array element with a sequence."
          ]
        }
      ]
    },
    {
      "metadata": {
        "trusted": true,
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      "cell_type": "code",
      "source": "## y shouldn't be initialized a variable. instead, use eval\ny = K.variable(np.zeros(5,))\ny *= 10\ny = x + 5 ## y is gone\nK.eval(y)",
      "execution_count": 5,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": "array([ 5.,  5.,  5.,  5.,  5.], dtype=float32)"
          },
          "metadata": {},
          "execution_count": 5
        }
      ]
    }
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        "description": "getting values from expressions in keras",
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